System and method for beam switching and reporting

ABSTRACT

A UE may receive a beam modification command that indicates a set of transmit beam indexes corresponding to a set of transmit beams of a base station, and each transmit beam index of the set of transmit beam indexes may indicate at least a transmit direction for transmitting a transmit beam by the base station. The UE may determine a set of receive beam indexes corresponding to receive beams of the UE based on the set of transmit beam indexes, and each receive beam index of the set of receive beam indexes may indicate at least a receive direction for receiving a receive beam by the UE. The UE may receive, from the base station, a signal through at least one receive beam corresponding to at least one receive beam index included in the set of receive beam indexes.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a Continuation of U.S. Non-Provisional applicationSer. No. 15/488,403, entitled SYSTEM AND METHOD FOR BEAM SWITCHING ANDREPORTING″ and filed on Apr. 14, 2017, which claims priority of U.S.Provisional application No. 62/342,174, entitled “BEAMMODIFICATION/SWITCHING PROCEDURES, BEAM STATE INFORMATION REPORTINGPROCEDURES, AND BEAM STATE INFORMATION REPORTING DURING RANDOM ACCESS”and filed on May 26, 2016, and U.S. Provisional application Ser. No.62/343,798, entitled “BEAM MODIFICATION/SWITCHING PROCEDURES, BEAM STATEINFORMATION REPORTING PROCEDURES, AND BEAM STATE INFORMATION REPORTINGDURING RANDOM ACCESS” and filed on May 31, 2016. The disclosures of theaforementioned applications are expressly incorporated by referenceherein in their entireties.

BACKGROUND Field

The present disclosure relates generally to communication systems, andmore particularly, to a user equipment and a base station that maycommunicate through one of more beams.

Background

Wireless communication systems are widely deployed to provide varioustelecommunication services such as telephony, video, data, messaging,and broadcasts. Typical wireless communication systems may employmultiple-access technologies capable of supporting communication withmultiple users by sharing available system resources. Examples of suchmultiple-access technologies include code division multiple access(CDMA) systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, orthogonal frequency divisionmultiple access (OFDMA) systems, single-carrier frequency divisionmultiple access (SC-FDMA) systems, and time division synchronous codedivision multiple access (TD-SCDMA) systems.

These multiple access technologies have been adopted in varioustelecommunication standards to provide a common protocol that enablesdifferent wireless devices to communicate on a municipal, national,regional, and even global level. An example telecommunication standardis Long Term Evolution (LTE). LTE is a set of enhancements to theUniversal Mobile Telecommunications System (UMTS) mobile standardpromulgated by Third Generation Partnership Project (3GPP). LTE isdesigned to support mobile broadband access through improved spectralefficiency, lowered costs, and improved services using OFDMA on thedownlink, SC-FDMA on the uplink, and multiple-input multiple-output(MIMO) antenna technology. However, as the demand for mobile broadbandaccess continues to increase, there exists a need for furtherimprovements in LTE technology. These improvements may also beapplicable to other multi-access technologies and the telecommunicationstandards that employ these technologies.

An example of an improvement to LTE may include fifth generationwireless systems and mobile networks (5G). 5G is a telecommunicationsstandard that may extend beyond LTE and/or 4G standards. For example, 5Gmay offer higher capacity and, therefore, serve a larger number of usersin an area. Further, 5G may improve data consumption and data rates.

SUMMARY

The following presents a simplified summary of one or more aspects inorder to provide a basic understanding of such aspects. This summary isnot an extensive overview of all contemplated aspects, and is intendedto neither identify key or critical elements of all aspects nordelineate the scope of any or all aspects. Its sole purpose is topresent some concepts of one or more aspects in a simplified form as aprelude to the more detailed description that is presented later.

Path loss may be relatively high in millimeter wave (mmW) systems.Transmission may be directional to mitigate path loss. A base stationmay transmit one or more beam reference signals by sweeping in alldirections so that a user equipment (UE) may identify a best “coarse”beam. Further, the base station may transmit a beam refinement requestsignal so that the UE may track “fine” beams. If a “coarse” beamidentified by the UE changes, the UE may need to inform the base stationso that the base station may train one or more new “fine” beams for theUE.

In a first aspect, a first method, first apparatus, and firstcomputer-readable medium are provided. The first apparatus may receive,from a base station, a contention resolution message, the contentionresolution message indicating at least a beam index corresponding to abeam. The first apparatus may determine whether the beam index isapplicable to the first apparatus. The first apparatus may communicatewith the base station through the beam corresponding to the beam indexwhen the beam index is applicable to the first apparatus. The firstapparatus may transmit, to the base station, an acknowledgement messagewhen the beam index is determined to be applicable to the firstapparatus. In an aspect, the contention resolution message is associatedwith a random access procedure. In an aspect, the determination ofwhether the beam index is applicable to the first apparatus includesattempting to decode the contention resolution message based on a radionetwork temporary identifier (RNTI) associated with the first apparatus,and the beam index is determined to be applicable to the first apparatuswhen the contention resolution message is successfully decoded. In anaspect, the first apparatus may refrain from transmitting anon-acknowledgement message to the base station when the beam index isdetermined to be inapplicable to the first apparatus or if thecontention resolution message is unsuccessfully decoded. In an aspect,the contention resolution message further includes an indication of oneor more channels associated with the beam index, and the communicationwith the base station through the beam corresponding to the beam indexis performed on the one or more indicated channels. In an aspect, thefirst apparatus may transmit, to the base station, a random accesspreamble. The first apparatus may receive, from the base station, arandom access response based on the random access preamble. The firstapparatus may transmit, to the base station, a connection requestmessage based on the random access response, and the contentionresolution message is transmitted based on the connection requestmessage.

In a second aspect, a second method, second apparatus, and secondcomputer-readable medium are provided. The second apparatus maytransmit, to a UE, a contention resolution message, and the contentionresolution message may indicate at least a beam index corresponding to abeam and indicating that the beam index is applicable to the UE. Thesecond apparatus may determine whether an acknowledgement message isreceived from the UE in response to the contention resolution message.The second apparatus may communicate with the UE through the beamcorresponding to the beam index when the acknowledgement message isdetermined to be received from the UE. In an aspect, the contentionresolution message is associated with a random access procedure. In anaspect, the second apparatus may scrambling at least a portion of thecontention resolution message using an RNTI associated the UE. In anaspect, the contention resolution message further includes an indicationof one or more channels associated with the beam index, and thecommunication with the UE through the beam corresponding to the beamindex is performed on the one or more indicated channels. In an aspect,the second apparatus may communicate with the UE through a serving beambefore transmission of the contention resolution message, and thecommunication with the UE continues through the serving beam based on anabsence of an acknowledgement message from the UE. The second apparatusmay receive, from the UE, a random access preamble. In an aspect, thesecond apparatus may transmit, to the UE, a random access response basedon the random access preamble. The second apparatus may receive, fromthe UE, a connection request message based on the random accessresponse, and the contention resolution message is transmitted based onthe connection request message.

In a third aspect, a third method, third apparatus, and thirdcomputer-readable medium are provided. The third apparatus may receive,from a base station, a beam modification command indicating at least onebeam index for communicating through at least one beam on at least onechannel, each beam index of the at least one beam index indicating atleast a direction for communicating through a corresponding beam of theat least one beam. The third apparatus may communicate, with the basestation, through the at least one beam corresponding to the at least onebeam index on the at least one channel. The third apparatus maycommunicate, with the base station, through a serving beam correspondingto a serving beam index, and switch, after receiving the beammodification command, from the serving beam to the at least one beamcorresponding to the at least one beam index indicated by the beammodification command. In an aspect, the switching from the serving beamto the at least one beam is performed at a predetermined time. In anaspect, the predetermined time is associated with at least one of asymbol or subframe, and wherein the beam modification command indicatesthe at least one of the symbol or the subframe. In an aspect, the beammodification command indicates, for each beam index of the at least onebeam index, a corresponding channel of the at least one channel. In anaspect, the at least one beam index comprises a plurality of beamindexes, and the at least one channel comprises a plurality of channels.In an aspect, the at least one beam index is applicable to one of uplinkcommunication or downlink communication. In an aspect, the beammodification command is received in a medium access control (MAC)control element (CE). In an aspect, the beam modification command isreceived in a downlink control information (DCI) message. In an aspect,the third apparatus may determine the at least one channel based on aDCI format of the DCI message. In an aspect, the beam modificationcommand is received via radio resource control (RRC) signaling.

In a fourth aspect, a fourth method, fourth apparatus, and fourthcomputer-readable medium are provided. The fourth apparatus may receivea beam modification command that indicates a set of transmit beamindexes corresponding to a set of transmit beams of a base station, andeach transmit beam index of the set of transmit beam indexes mayindicate at least a transmit direction for transmitting a transmit beamby the base station. The fourth apparatus may determine a set of receivebeam indexes corresponding to receive beams of the fourth apparatusbased on the set of transmit beam indexes, each receive beam index ofthe set of receive beam indexes indicating at least a receive directionfor receiving a receive beam by the fourth apparatus. The fourthapparatus may receive, from the base station, a beam refinementreference signal (BRRS) through at least one receive beam correspondingto at least one receive beam index included in the set of receive beamindexes. In an aspect, the receiving, from the base station, the BRRSthrough the at least one receive beam corresponding to the at least onereceive beam index included in the set of receive beam indexes includesreceiving a first portion of the BRRS in a first set of symbols througha first receive beam corresponding to a first receive beam indexincluded in the set of receive beam indexes, and receiving a secondportion of the BRRS in a second set of symbols through a second receivebeam corresponding to a second receive beam index included in the set ofreceive beam indexes. In an aspect, the BRRS is received in one or moresymbols corresponding to one or more symbol indexes. In an aspect, thebeam modification command indicates the one or more symbol indexes, anda corresponding transmit beam index of the set of transmit beam indexesfor each symbol index of the one or more symbol indexes. In an aspect,the one or more symbol indexes in which the BRRS is received arepredetermined. In an aspect, the BRRS is received through the set oftransmit beams from the base station corresponding to the set oftransmit beam indexes. In an aspect, the BRRS is received through adifferent set of transmit beams from the base station than the set oftransmit beams corresponding to the set of transmit beam indexes, thedifferent set of transmit beams corresponding to a second set oftransmit beam indexes different from the set of transmit beam indexes.In an aspect, the beam modification command is received in a MAC CE. Inan aspect, the beam modification command is received in a DCI message.In an aspect, the beam modification command is received via RRCsignaling.

In a fifth aspect, a fifth method, fifth apparatus, and fifthcomputer-readable medium are provided. The fifth apparatus may receive,from a base station, through a set of beams a set of beam referencesignals (BRSs). The fifth apparatus may measure a signal quality of eachBRS of the set of BRSs, each measured signal quality corresponding to abeam of the set of beams. In an aspect, the fifth apparatus may maintaina set of candidate beam indexes corresponding to a set of best measuredsignal qualities of the set of BRSs. In an aspect, the fifth apparatusmay transmit, to the base station, beam state information (BSI)indicating at least one measured signal quality and at least one beamindex from the set of maintained candidate beam indexes, the at leastone beam index corresponding to the at least one measured signalquality. In an aspect, the set of the best measured signal qualities isa set of the highest measured signal qualities. In an aspect, Ncandidate beam indexes are maintained in the set of candidate beamindexes, N being predetermined. In an aspect, the set of best measuredsignal qualities of the set of BRSs is based on a most recent set ofsignal qualities of the set of BRSs, a filtered set of signal qualitiesof the set of BRSs, or a time-averaged set of signal qualities of theset of BRSs. In an aspect, the maintenance of the set of candidate beamindexes is based on at least one hysteresis criteria for including abeam index in or excluding a beam index from the set of candidate beamindexes. In an aspect, the fifth apparatus may receive, from the basestation, an indication of one or more beam indexes that are to beexcluded from the maintained set of candidate beam indexes. In anaspect, the signal quality comprises at least one of a beam referencesignal received power (BRSRP), a beam reference signal received quality(BRSRQ), a signal-to interference radio (SIR), asignal-to-interference-plus noise ratio (SINR), or a signal-to-noiseratio (SNR).

In a sixth aspect, a sixth method, sixth apparatus, and sixthcomputer-readable medium are provided. The sixth apparatus may receive,from a base station, a message requesting BSI. The sixth apparatus maydetermine a number N of BSI reports to send to the base station, andeach BSI report may indicate a beam index corresponding to a beam and areceived power associated with the beam. The sixth apparatus may send,to the base station, N BSI reports based on the message requesting BSI.The sixth apparatus may receive, from the base station, a set of signalsthrough a set of beams, and determine the received power for each signalof the set of signals received through each beam of the set of beams,each received power associated with a beam of the set of beams. In anaspect, the N BSI reports include N received powers corresponding to thehighest determined received powers. In an aspect, the determination ofthe number N of BSI reports to send to the base station is based on atype of the message requesting the BSI. In an aspect, the type of themessage requesting the BSI comprises a DCI message. In an aspect, thenumber N of BSI reports to send to the base station is determined to beone based on the DCI message. In an aspect, the determined number N ofBSI reports are sent on a physical uplink control channel (PUCCH). In anaspect, the type of message requesting the BSI comprises a random accessresponse (RAR) message. In an aspect, the number N of BSI reports isdetermined to be greater than one based on the RAR message. In anaspect, the determined number N of BSI reports are sent on a physicaluplink shared channel (PUSCH).

In a seventh aspect, a seventh method, seventh apparatus, and seventhcomputer-readable medium are provided. The seventh apparatus may selecta first beam for communication with a base station. The seventhapparatus may attempt, through the selected first beam, at least onerandom access channel (RACH) procedure with the base station. Theseventh apparatus may determine that the at least one RACH procedurefailed with the base station. The seventh apparatus may send, after asuccessful RACH procedure with the base station, information indicatingthat the at least one RACH procedure failed. In an aspect, the seventhapparatus may select a new beam for communication with the base stationafter the determination that the at least one RACH procedure failed, andat least a portion of the successful RACH procedure is performed throughthe selected new beam. In an aspect, the seventh apparatus may increasea transmission power after the determination that the at least one RACHprocedure failed, and at least a portion of the successful RACHprocedure is performed with the increased transmission power. In anaspect, the seventh apparatus may store information associated with theselected first beam based on the determination that the at least oneRACH procedure failed. In an aspect, the information indicating that theat least one RACH procedure failed includes the stored informationassociated with the first beam. In an aspect, the information indicatingthat the at least one RACH procedure failed includes an indication of asubframe in which a RACH message associated with the at least one RACHprocedure is carried. In an aspect, the seventh apparatus may excludethe selected first beam from a candidate beam set maintained by the UEbased on the determination that the at least one RACH procedure failed.In an aspect, the information indicating that the at least one RACHprocedure failed comprises a BSI report. In an aspect, the at least oneRACH procedure includes at least one of transmitting, to the basestation, a random access preamble, receiving, from the base station, arandom access response based on the random access preamble,transmitting, to the base station, a connection request message based onthe random access response, and/or receive a contention resolutionmessage based on the connection request message. In an aspect, theseventh apparatus is synchronized with a network that includes the basestation based on the successful RACH procedure.

To the accomplishment of the foregoing and related ends, the one or moreaspects comprise the features hereinafter fully described andparticularly pointed out in the claims. The following description andthe annexed drawings set forth in detail certain illustrative featuresof the one or more aspects. These features are indicative, however, ofbut a few of the various ways in which the principles of various aspectsmay be employed, and this description is intended to include all suchaspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a wireless communicationssystem and an access network.

FIGS. 2A, 2B, 2C, and 2D are diagrams illustrating LTE examples of a DLframe structure, DL channels within the DL frame structure, an UL framestructure, and UL channels within the UL frame structure, respectively.

FIG. 3 is a diagram illustrating an example of a base station and userequipment (UE) in an access network.

FIGS. 4A and 4B are call flow diagrams of a wireless communicationssystem.

FIGS. 5A through 5G illustrate diagrams of a wireless communicationssystem.

FIG. 6 is a diagram of a wireless communications system.

FIG. 7 is a diagram of a wireless communications system.

FIG. 8 is a diagram of a wireless communications system.

FIG. 9 is a diagram of a wireless communications system.

FIG. 10 is a diagram of a wireless communications system.

FIG. 11 is a diagram of a wireless communications system.

FIG. 12 is a flowchart of a method of wireless communication.

FIG. 13 is a flowchart of a method of wireless communication.

FIG. 14 is a flowchart of a method of wireless communication.

FIG. 15 is a flowchart of a method of wireless communication.

FIG. 16 is a flowchart of a method of wireless communication.

FIG. 17 is a flowchart of a method of wireless communication.

FIG. 18 is a flowchart of a method of wireless communication.

FIG. 19 is a conceptual data flow diagram illustrating the data flowbetween different means/components in an exemplary apparatus.

FIG. 20 is a diagram illustrating an example of a hardwareimplementation for an apparatus employing a processing system.

FIG. 21 is a conceptual data flow diagram illustrating the data flowbetween different means/components in an exemplary apparatus.

FIG. 22 is a diagram illustrating an example of a hardwareimplementation for an apparatus employing a processing system.

FIG. 23 is a conceptual data flow diagram illustrating the data flowbetween different means/components in an exemplary apparatus.

FIG. 24 is a diagram illustrating an example of a hardwareimplementation for an apparatus employing a processing system.

FIG. 25 is a conceptual data flow diagram illustrating the data flowbetween different means/components in an exemplary apparatus.

FIG. 26 is a diagram illustrating an example of a hardwareimplementation for an apparatus employing a processing system.

FIG. 27 is a conceptual data flow diagram illustrating the data flowbetween different means/components in an exemplary apparatus.

FIG. 28 is a diagram illustrating an example of a hardwareimplementation for an apparatus employing a processing system.

FIG. 29 is a conceptual data flow diagram illustrating the data flowbetween different means/components in an exemplary apparatus.

FIG. 30 is a diagram illustrating an example of a hardwareimplementation for an apparatus employing a processing system.

FIG. 31 is a conceptual data flow diagram illustrating the data flowbetween different means/components in an exemplary apparatus.

FIG. 32 is a diagram illustrating an example of a hardwareimplementation for an apparatus employing a processing system.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appendeddrawings is intended as a description of various configurations and isnot intended to represent the only configurations in which the conceptsdescribed herein may be practiced. The detailed description includesspecific details for the purpose of providing a thorough understandingof various concepts. However, it will be apparent to those skilled inthe art that these concepts may be practiced without these specificdetails. In some instances, well known structures and components areshown in block diagram form in order to avoid obscuring such concepts.

Several aspects of telecommunication systems will now be presented withreference to various apparatus and methods. These apparatus and methodswill be described in the following detailed description and illustratedin the accompanying drawings by various blocks, components, circuits,processes, algorithms, etc. (collectively referred to as “elements”).These elements may be implemented using electronic hardware, computersoftware, or any combination thereof. Whether such elements areimplemented as hardware or software depends upon the particularapplication and design constraints imposed on the overall system.

By way of example, an element, or any portion of an element, or anycombination of elements may be implemented as a “processing system” thatincludes one or more processors. Examples of processors includemicroprocessors, microcontrollers, graphics processing units (GPUs),central processing units (CPUs), application processors, digital signalprocessors (DSPs), reduced instruction set computing (RISC) processors,systems on a chip (SoC), baseband processors, field programmable gatearrays (FPGAs), programmable logic devices (PLDs), state machines, gatedlogic, discrete hardware circuits, and other suitable hardwareconfigured to perform the various functionality described throughoutthis disclosure. One or more processors in the processing system mayexecute software. Software shall be construed broadly to meaninstructions, instruction sets, code, code segments, program code,programs, subprograms, software components, applications, softwareapplications, software packages, routines, subroutines, objects,executables, threads of execution, procedures, functions, etc., whetherreferred to as software, firmware, middleware, microcode, hardwaredescription language, or otherwise.

Accordingly, in one or more example embodiments, the functions describedmay be implemented in hardware, software, or any combination thereof. Ifimplemented in software, the functions may be stored on or encoded asone or more instructions or code on a computer-readable medium.Computer-readable media includes computer storage media. Storage mediamay be any available media that can be accessed by a computer. By way ofexample, and not limitation, such computer-readable media can comprise arandom-access memory (RAM), a read-only memory (ROM), an electricallyerasable programmable ROM (EEPROM), optical disk storage, magnetic diskstorage, other magnetic storage devices, combinations of theaforementioned types of computer-readable media, or any other mediumthat can be used to store computer executable code in the form ofinstructions or data structures that can be accessed by a computer.

FIG. 1 is a diagram illustrating an example of a wireless communicationssystem and an access network 100. The wireless communications system(also referred to as a wireless wide area network (WWAN)) includes basestations 102, UEs 104, and an Evolved Packet Core (EPC) 160. The basestations 102 may include macro cells (high power cellular base station)and/or small cells (low power cellular base station). The macro cellsinclude eNBs. The small cells include femtocells, picocells, andmicrocells.

The base stations 102 (collectively referred to as Evolved UniversalMobile Telecommunications System (UMTS) Terrestrial Radio Access Network(E-UTRAN)) interface with the EPC 160 through backhaul links 132 (e.g.,S1 interface). In addition to other functions, the base stations 102 mayperform one or more of the following functions: transfer of user data,radio channel ciphering and deciphering, integrity protection, headercompression, mobility control functions (e.g., handover, dualconnectivity), inter-cell interference coordination, connection setupand release, load balancing, distribution for non-access stratum (NAS)messages, NAS node selection, synchronization, radio access network(RAN) sharing, multimedia broadcast multicast service (MBMS), subscriberand equipment trace, RAN information management (RIM), paging,positioning, and delivery of warning messages. The base stations 102 maycommunicate directly or indirectly (e.g., through the EPC 160) with eachother over backhaul links 134 (e.g., X2 interface). The backhaul links134 may be wired or wireless.

The base stations 102 may wirelessly communicate with the UEs 104. Eachof the base stations 102 may provide communication coverage for arespective geographic coverage area 110. There may be overlappinggeographic coverage areas 110. For example, the small cell 102′ may havea coverage area 110′ that overlaps the coverage area 110 of one or moremacro base stations 102. A network that includes both small cell andmacro cells may be known as a heterogeneous network. A heterogeneousnetwork may also include Home Evolved Node Bs (eNBs) (HeNBs), which mayprovide service to a restricted group known as a closed subscriber group(CSG). The communication links 120 between the base stations 102 and theUEs 104 may include uplink (UL) (also referred to as reverse link)transmissions from a UE 104 to a base station 102 and/or downlink (DL)(also referred to as forward link) transmissions from a base station 102to a UE 104. The communication links 120 may use MIMO antennatechnology, including spatial multiplexing, beamforming, and/or transmitdiversity. The communication links may be through one or more carriers.The base stations 102/UEs 104 may use spectrum up to Y MHz (e.g., 5, 10,15, 20 MHz) bandwidth per carrier allocated in a carrier aggregation ofup to a total of Yx MHz (x component carriers) used for transmission ineach direction. The carriers may or may not be adjacent to each other.Allocation of carriers may be asymmetric with respect to DL and UL(e.g., more or less carriers may be allocated for DL than for UL). Thecomponent carriers may include a primary component carrier and one ormore secondary component carriers. A primary component carrier may bereferred to as a primary cell (PCell) and a secondary component carriermay be referred to as a secondary cell (SCell).

The wireless communications system may further include a Wi-Fi accesspoint (AP) 150 in communication with Wi-Fi stations (STAs) 152 viacommunication links 154 in a 5 gigahertz (GHz) unlicensed frequencyspectrum. When communicating in an unlicensed frequency spectrum, theSTAs 152/AP 150 may perform a clear channel assessment (CCA) prior tocommunicating in order to determine whether the channel is available.

The small cell 102′ may operate in a licensed and/or an unlicensedfrequency spectrum. When operating in an unlicensed frequency spectrum,the small cell 102′ may employ LTE and use the same 5 GHz unlicensedfrequency spectrum as used by the Wi-Fi AP 150. The small cell 102′,employing LTE in an unlicensed frequency spectrum, may boost coverage toand/or increase capacity of the access network. LTE in an unlicensedspectrum may be referred to as LTE-unlicensed (LTE-U), licensed assistedaccess (LAA), or MuLTEfire.

The millimeter wave (mmW) base station 180 may operate in mmWfrequencies and/or near mmW frequencies in communication with the UE182. In one aspect, the UE 182 may be an aspect of the UE 104. Extremelyhigh frequency (EHF) is part of the RF in the electromagnetic spectrum.EHF has a range of 30 GHz to 300 GHz and a wavelength between 1millimeter and 10 millimeters. Radio waves in the band may be referredto as a millimeter wave. Near mmW may extend down to a frequency of 3GHz with a wavelength of 100 millimeters. The super high frequency (SHF)band extends between 3 GHz and 30 GHz, also referred to as centimeterwave. Communications using the mmW/near mmW radio frequency band hasextremely high path loss and a short range. The mmW base station 180 mayutilize beamforming 184 with the UE 182 to compensate for the extremelyhigh path loss and short range.

The EPC 160 may include a Mobility Management Entity (MME) 162, otherMMEs 164, a Serving Gateway 166, a Multimedia Broadcast MulticastService (MBMS) Gateway 168, a Broadcast Multicast Service Center (BM-SC)170, and a Packet Data Network (PDN) Gateway 172. The MME 162 may be incommunication with a Home Subscriber Server (HSS) 174. The MME 162 isthe control node that processes the signaling between the UEs 104 andthe EPC 160. Generally, the MME 162 provides bearer and connectionmanagement. All user Internet protocol (IP) packets are transferredthrough the Serving Gateway 166, which itself is connected to the PDNGateway 172. The PDN Gateway 172 provides UE IP address allocation aswell as other functions. The PDN Gateway 172 and the BM-SC 170 areconnected to the IP Services 176. The IP Services 176 may include theInternet, an intranet, an IP Multimedia Subsystem (IMS), a PS StreamingService (PSS), and/or other IP services. The BM-SC 170 may providefunctions for MBMS user service provisioning and delivery. The BM-SC 170may serve as an entry point for content provider MBMS transmission, maybe used to authorize and initiate MBMS Bearer Services within a publicland mobile network (PLMN), and may be used to schedule MBMStransmissions. The MBMS Gateway 168 may be used to distribute MBMStraffic to the base stations 102 belonging to a Multicast BroadcastSingle Frequency Network (MBSFN) area broadcasting a particular service,and may be responsible for session management (start/stop) and forcollecting eMBMS related charging information.

The base station may also be referred to as a Node B, evolved Node B(eNB), an access point, a base transceiver station, a radio basestation, a radio transceiver, a transceiver function, a basic serviceset (BSS), an extended service set (ESS), or some other suitableterminology. The base station 102 provides an access point to the EPC160 for a UE 104. Examples of UEs 104 include a cellular phone, a smartphone, a session initiation protocol (SIP) phone, a laptop, a personaldigital assistant (PDA), a satellite radio, a global positioning system,a multimedia device, a video device, a digital audio player (e.g., MP3player), a camera, a game console, a tablet, a smart device, a wearabledevice, or any other similar functioning device. The UE 104 may also bereferred to as a station, a mobile station, a subscriber station, amobile unit, a subscriber unit, a wireless unit, a remote unit, a mobiledevice, a wireless device, a wireless communications device, a remotedevice, a mobile subscriber station, an access terminal, a mobileterminal, a wireless terminal, a remote terminal, a handset, a useragent, a mobile client, a client, or some other suitable terminology.

Referring again to FIG. 1, in certain aspects, the UE 104 may receive abeam modification command 198 that indicates a set of transmit beamindexes corresponding to a set of transmit beams of a base station(e.g., the base station 102 and/or the mmW base station 180), and eachtransmit beam index of the set of transmit beam indexes may indicate atleast a transmit direction for transmitting a transmit beam by the basestation. The UE 104 may determine a set of receive beam indexescorresponding to receive beams of the UE 104 based on the set oftransmit beam indexes, and each receive beam index of the set of receivebeam indexes may indicate at least a receive direction for receiving areceive beam by the UE 104. The UE 104 may receive, from the basestation (e.g., the base station 102 and/or the mmW base station 180), aBRRS through at least one receive beam corresponding to at least onereceive beam index included in the set of receive beam indexes. In anaspect, the UE 104 may receive a first portion of the BRRS in a firstset of symbols through a first receive beam corresponding to a firstreceive beam index included in the set of receive beam indexes, and theUE 104 may receive a second portion of the BRRS in a second set ofsymbols through a second receive beam corresponding to a second receivebeam index included in the set of receive beam indexes. In an aspect,the BRRS may be received in one or more symbols corresponding to one ormore symbol indexes. In an aspect, the beam modification command 198indicates the one or more symbol indexes, and a corresponding transmitbeam index of the set of transmit beam indexes for each symbol index ofthe one or more symbol indexes. In an aspect, the one or more symbolindexes in which the BRRS is received are predetermined. In an aspect,the BRRS is received through the set of transmit beams from the basestation (e.g., the base station 102 and/or the mmW base station 180)corresponding to the set of transmit beam indexes. In an aspect, theBRRS is received through a different set of transmit beams from the basestation (e.g., the base station 102 and/or the mmW base station 180)than the set of transmit beams corresponding to the set of transmit beamindexes, the different set of transmit beams corresponding to a secondset of transmit beam indexes different from the set of transmit beamindexes. In an aspect, the beam modification command 198 is received ina MAC CE. In an aspect, the beam modification command 198 is received ina DCI message. In an aspect, the beam modification command 198 isreceived via RRC signaling.

FIG. 2A is a diagram 200 illustrating an example of a DL frame structurein LTE. FIG. 2B is a diagram 230 illustrating an example of channelswithin the DL frame structure in LTE. FIG. 2C is a diagram 250illustrating an example of an UL frame structure in LTE. FIG. 2D is adiagram 280 illustrating an example of channels within the UL framestructure in LTE. Other wireless communication technologies may have adifferent frame structure and/or different channels. In LTE, a frame (10ms) may be divided into 10 equally sized subframes.

In 5G, a frame may be less than 10 ms (and a subframe may be referred toas a slot, which may include one or more minislots). The structure is tobe regarded as illustrative, and a subframe may be referred to a slot ora minislot. A slot may one-fourth to one-fifth of a subframe (e.g., ofan LTE subframe) and a minislot may include 1 to 7 OFDM symbols. Eachsubframe may include two consecutive time slots.

A resource grid may be used to represent the two time slots, each timeslot including one or more time concurrent resource blocks (RBs) (alsoreferred to as physical RBs (PRBs)). The resource grid is divided intomultiple resource elements (REs). In LTE, for a normal cyclic prefix, anRB contains 12 consecutive subcarriers in the frequency domain and 7consecutive symbols (for DL, OFDM symbols; for UL, SC-FDMA symbols) inthe time domain, for a total of 84 REs. For an extended cyclic prefix,an RB contains 12 consecutive subcarriers in the frequency domain and 6consecutive symbols in the time domain, for a total of 72 REs. Thenumber of bits carried by each RE depends on the modulation scheme.

As illustrated in FIG. 2A, some of the REs carry DL reference (pilot)signals (DL-RS) for channel estimation at the UE. The DL-RS may includecell-specific reference signals (CRS) (also sometimes called common RS),UE-specific reference signals (UE-RS), and channel state informationreference signals (CSI-RS). FIG. 2A illustrates CRS for antenna ports 0,1, 2, and 3 (indicated as R₀, R₁, R₂, and R₃, respectively), UE-RS forantenna port 5 (indicated as R₅), and CSI-RS for antenna port 15(indicated as R). FIG. 2B illustrates an example of various channelswithin a DL subframe of a frame. The physical control format indicatorchannel (PCFICH) is within symbol 0 of slot 0, and carries a controlformat indicator (CFI) that indicates whether the physical downlinkcontrol channel (PDCCH) occupies 1, 2, or 3 symbols (FIG. 2B illustratesa PDCCH that occupies 3 symbols). The PDCCH carries downlink controlinformation (DCI) within one or more control channel elements (CCEs),each CCE including nine RE groups (REGs), each REG including fourconsecutive REs in an OFDM symbol. A UE may be configured with aUE-specific enhanced PDCCH (ePDCCH) that also carries DCI. The ePDCCHmay have 2, 4, or 8 RB pairs (FIG. 2B shows two RB pairs, each subsetincluding one RB pair). The physical hybrid automatic repeat request(ARQ) (HARQ) indicator channel (PHICH) is also within symbol 0 of slot 0and carries the HARQ indicator (HI) that indicates HARQ acknowledgment(ACK)/negative ACK (NACK) feedback based on the physical uplink sharedchannel (PUSCH). The primary synchronization channel (PSCH) is withinsymbol 6 of slot 0 within subframes 0 and 5 of a frame, and carries aprimary synchronization signal (PSS) that is used by a UE to determinesubframe timing and a physical layer identity. The secondarysynchronization channel (SSCH) is within symbol 5 of slot 0 withinsubframes 0 and 5 of a frame, and carries a secondary synchronizationsignal (SSS) that is used by a UE to determine a physical layer cellidentity group number. Based on the physical layer identity and thephysical layer cell identity group number, the UE can determine aphysical cell identifier (PCI). Based on the PCI, the UE can determinethe locations of the aforementioned DL-RS. The physical broadcastchannel (PBCH) is within symbols 0, 1, 2, 3 of slot 1 of subframe 0 of aframe, and carries a master information block (MIB). The MIB provides anumber of RBs in the DL system bandwidth, a PHICH configuration, and asystem frame number (SFN). The physical downlink shared channel (PDSCH)carries user data, broadcast system information not transmitted throughthe PBCH such as system information blocks (SIBs), and paging messages.

As illustrated in FIG. 2C, some of the REs carry demodulation referencesignals (DM-RS) for channel estimation at the eNB. The UE mayadditionally transmit sounding reference signals (SRS) in the lastsymbol of a subframe. The SRS may have a comb structure, and a UE maytransmit SRS on one of the combs. The SRS may be used by an eNB forchannel quality estimation to enable frequency-dependent scheduling onthe UL. FIG. 2D illustrates an example of various channels within an ULsubframe of a frame. A physical random access channel (PRACH) may bewithin one or more subframes within a frame based on the PRACHconfiguration. The PRACH may include six consecutive RB pairs within asubframe. The PRACH allows the UE to perform initial system access andachieve UL synchronization. A physical uplink control channel (PUCCH)may be located on edges of the UL system bandwidth. The PUCCH carriesuplink control information (UCI), such as scheduling requests, a channelquality indicator (CQI), a precoding matrix indicator (PMI), a rankindicator (RI), and HARQ ACK/NACK feedback. The PUSCH carries data, andmay additionally be used to carry a buffer status report (BSR), a powerheadroom report (PHR), and/or UCI.

FIG. 3 is a block diagram of an base station 310 in communication with aUE 350 in an access network. In an aspect, the base station 310 may bean aspect of the mmW base station 180 and/or the base station 102. Inthe DL, IP packets from the EPC 160 may be provided to acontroller/processor 375. The controller/processor 375 implements layer3 and layer 2 functionality. Layer 3 includes a radio resource control(RRC) layer, and layer 2 includes a packet data convergence protocol(PDCP) layer, a radio link control (RLC) layer, and a medium accesscontrol (MAC) layer. The controller/processor 375 provides RRC layerfunctionality associated with broadcasting of system information (e.g.,MIB, SIBs), RRC connection control (e.g., RRC connection paging, RRCconnection establishment, RRC connection modification, and RRCconnection release), inter radio access technology (RAT) mobility, andmeasurement configuration for UE measurement reporting; PDCP layerfunctionality associated with header compression/decompression, security(ciphering, deciphering, integrity protection, integrity verification),and handover support functions; RLC layer functionality associated withthe transfer of upper layer packet data units (PDUs), error correctionthrough ARQ, concatenation, segmentation, and reassembly of RLC servicedata units (SDUs), re-segmentation of RLC data PDUs, and reordering ofRLC data PDUs; and MAC layer functionality associated with mappingbetween logical channels and transport channels, multiplexing of MACSDUs onto transport blocks (TBs), demultiplexing of MAC SDUs from TBs,scheduling information reporting, error correction through HARQ,priority handling, and logical channel prioritization.

The transmit (TX) processor 316 and the receive (RX) processor 370implement layer 1 functionality associated with various signalprocessing functions. Layer 1, which includes a physical (PHY) layer,may include error detection on the transport channels, forward errorcorrection (FEC) coding/decoding of the transport channels,interleaving, rate matching, mapping onto physical channels,modulation/demodulation of physical channels, and MIMO antennaprocessing. The TX processor 316 handles mapping to signalconstellations based on various modulation schemes (e.g., binaryphase-shift keying (BPSK), quadrature phase-shift keying (QPSK),M-phase-shift keying (M-PSK), M-quadrature amplitude modulation(M-QAM)). The coded and modulated symbols may then be split intoparallel streams. Each stream may then be mapped to an OFDM subcarrier,multiplexed with a reference signal (e.g., pilot) in the time and/orfrequency domain, and then combined together using an Inverse FastFourier Transform (IFFT) to produce a physical channel carrying a timedomain OFDM symbol stream. The OFDM stream is spatially precoded toproduce multiple spatial streams. Channel estimates from a channelestimator 374 may be used to determine the coding and modulation scheme,as well as for spatial processing. The channel estimate may be derivedfrom a reference signal and/or channel condition feedback transmitted bythe UE 350. Each spatial stream may then be provided to a differentantenna 320 via a separate transmitter 318TX. Each transmitter 318TX maymodulate an RF carrier with a respective spatial stream fortransmission.

At the UE 350, each receiver 354RX receives a signal through itsrespective antenna 352. Each receiver 354RX recovers informationmodulated onto an RF carrier and provides the information to the receive(RX) processor 356. The TX processor 368 and the RX processor 356implement layer 1 functionality associated with various signalprocessing functions. The RX processor 356 may perform spatialprocessing on the information to recover any spatial streams destinedfor the UE 350. If multiple spatial streams are destined for the UE 350,they may be combined by the RX processor 356 into a single OFDM symbolstream. The RX processor 356 then converts the OFDM symbol stream fromthe time-domain to the frequency domain using a Fast Fourier Transform(FFT). The frequency domain signal comprises a separate OFDM symbolstream for each subcarrier of the OFDM signal. The symbols on eachsubcarrier, and the reference signal, are recovered and demodulated bydetermining the most likely signal constellation points transmitted bythe base station 310. These soft decisions may be based on channelestimates computed by the channel estimator 358. The soft decisions arethen decoded and deinterleaved to recover the data and control signalsthat were originally transmitted by the base station 310 on the physicalchannel. The data and control signals are then provided to thecontroller/processor 359, which implements layer 3 and layer 2functionality.

The controller/processor 359 can be associated with a memory 360 thatstores program codes and data. The memory 360 may be referred to as acomputer-readable medium. In the UL, the controller/processor 359provides demultiplexing between transport and logical channels, packetreassembly, deciphering, header decompression, and control signalprocessing to recover IP packets from the EPC 160. Thecontroller/processor 359 is also responsible for error detection usingan ACK and/or NACK protocol to support HARQ operations.

Similar to the functionality described in connection with the DLtransmission by the base station 310, the controller/processor 359provides RRC layer functionality associated with system information(e.g., MIB, SIBs) acquisition, RRC connections, and measurementreporting; PDCP layer functionality associated with headercompression/decompression, and security (ciphering, deciphering,integrity protection, integrity verification); RLC layer functionalityassociated with the transfer of upper layer PDUs, error correctionthrough ARQ, concatenation, segmentation, and reassembly of RLC SDUs,re-segmentation of RLC data PDUs, and reordering of RLC data PDUs; andMAC layer functionality associated with mapping between logical channelsand transport channels, multiplexing of MAC SDUs onto TBs,demultiplexing of MAC SDUs from TBs, scheduling information reporting,error correction through HARQ, priority handling, and logical channelprioritization.

Channel estimates derived by a channel estimator 358 from a referencesignal or feedback transmitted by the base station 310 may be used bythe TX processor 368 to select the appropriate coding and modulationschemes, and to facilitate spatial processing. The spatial streamsgenerated by the TX processor 368 may be provided to different antenna352 via separate transmitters 354TX. Each transmitter 354TX may modulatean RF carrier with a respective spatial stream for transmission.

The UL transmission is processed at the base station 310 in a mannersimilar to that described in connection with the receiver function atthe UE 350. Each receiver 318RX receives a signal through its respectiveantenna 320. Each receiver 318RX recovers information modulated onto anRF carrier and provides the information to a RX processor 370.

The controller/processor 375 can be associated with a memory 376 thatstores program codes and data. The memory 376 may be referred to as acomputer-readable medium. In the UL, the controller/processor 375provides demultiplexing between transport and logical channels, packetreassembly, deciphering, header decompression, control signal processingto recover IP packets from the UE 350. IP packets from thecontroller/processor 375 may be provided to the EPC 160. Thecontroller/processor 375 is also responsible for error detection usingan ACK and/or NACK protocol to support HARQ operations.

FIGS. 4A and 4B illustrate call flow diagrams of methods 400, 440 ofRACH procedures. A UE 404 may perform a RACH procedure with a basestation 402 (e.g., a mmW base station, an eNB, etc.), for example, inorder to synchronize with a network. A RACH procedure may be eithercontention-based or non-contention based.

FIG. 4A illustrates a method 400 for a contention-based RACH procedure.First, the UE 404 may select a RACH preamble for the RACH procedure.Further, the UE 404 may determine a random access (RA) RNTI in order toidentify the UE 404 during the RACH procedure. The UE 404 may determinean RA-RNTI based on, for example, a time slot number in which a MSG1 410is sent. The UE 404 may include the RACH preamble and the RA-RNTI in theMSG1 410.

In an aspect, the UE 404 may determine at least one resource (e.g., atime and/or frequency resource) that is to carry the MSG1 410. Forexample, the base station 402 may broadcast system information (e.g., aSIB), and the UE 404 may acquire the at least one resource based on thesystem information (e.g., system information included in a SIB2). The UE404 may send the MSG1 410 to the base station 402, for example, on theat least one resource. If the UE 404 does not receive a response to theMSG1 410 (e.g., after expiration of a timer), then the UE 404 mayincrease transmit power (e.g., by a fixed interval) and resend the MSG1410.

Based on the MSG1 410, the base station 402 may send, to the UE 404, aMSG2 412. The MSG2 412 may also be known as a random access response andmay be sent on a downlink shared channel (DL-SCH). The base station 402may determine a temporary cell RNTI (T-CRNTI). Further, the base station402 may determine a timing advance value so that the UE 404 may adjusttiming to compensate for delay. Further, the base station 402 maydetermine an uplink resource grant, which may include an initialresource assignment for the UE 404 so that the UE 404 may use the uplinkshared channel (UL-SCH). The base station 402 may generate the MSG2 412to include the C-RNTI, the timing advance value, and/or the uplink grantresource. The base station 402 may then transmit the MSG2 412 to the UE404. In an aspect, the UE 404 may determine an uplink resource grantbased on the MSG2 412.

Based on the MSG2 412, the UE 404 may send, to the base station 402, aMSG3 414. The MSG3 414 may also be known as an RRC connection requestmessage and/or a scheduled transmission message. The UE 404 maydetermine a temporary mobile subscriber identity (TMSI) associated withthe UE 404 or another random value used to identify the UE 404 (e.g., ifthe UE 404 is connecting to the network for the first time). The UE 404may determine a connection establishment clause, which may indicate whythe UE 404 is connecting to the network. The UE 404 may generate theMSG3 414 to include at least the TMSI or other random value, as well asthe connection establishment clause. The UE 404 may then transmit theMSG3 414 to the base station on the UL-SCH.

Based on the MSG3 414, the base station 402 may send, to the UE 404, aMSG4 416. The MSG4 416 may also be known as a connection resolutionmessage. The base station 402 may address the MSG4 416 toward the TMSIor random value from the MSG3 414. The MSG4 416 may be scrambled with aC-RNTI associated with the UE 404. The base station 402 may transmit theMSG4 416 to the UE 404. The UE 404 may decode the MSG4 416, for example,using the C-RNTI associated with the UE 404. This RACH procedure mayallow the UE 404 to be synchronized with a network.

FIG. 4B illustrates a method 440 of a non-contention-based RACHprocedure. The non-contention-based RACH procedure may be applicable tohandover and/or downlink data arrival.

The base station 402 may determine a random access preamble assigned tothe UE 404. The base station 402 may transmit, to the UE 404, the randomaccess preamble assignment 442. The UE 404 may respond to the randomaccess preamble assignment 442 with the random access preamble 444(e.g., an RRC connection message), which may be the random accesspreamble assigned to the UE 404. The UE 404 may then receive, from thebase station 402, a random access response 446 (e.g., an uplink grant).

FIGS. 5A through 5G are diagrams illustrating an example of thetransmission of beamformed signals between a base station and a UE. Thebase station 502 may be embodied as a base station in a mmW system (mmWbase station), such as the mmW base station 180. In one aspect, the basestation 502 may be collocated with another base station, such as an eNB,a cellular base station, or other base station (e.g., a base stationconfigured to communicate in a sub-6 GHz band). While some beams areillustrated as adjacent to one another, such an arrangement may bedifferent in different aspects (e.g., beams transmitted during a samesymbol may not be adjacent to one another). Additionally, the number ofillustrated beams is to be regarded as illustrative.

Extremely high frequency (EHF) is part of the RF in the electromagneticspectrum. EHF has a range of 30 GHz to 300 GHz and a wavelength between1 millimeter and 10 millimeters. Radio waves in the band may be referredto as a millimeter wave. Near mmW may extend down to a frequency of 3GHz with a wavelength of 100 millimeters (the super high frequency (SHF)band extends between 3 GHz and 30 GHz, also referred to as centimeterwave). While the disclosure herein refers to mmWs, it should beunderstood that the disclosure also applies to near mmWs. Further, whilethe disclosure herein refers to mmW base stations, it should beunderstood that the disclosure also applies to near-mmW base stations.

In order to build a useful communication network in the millimeterwavelength spectrum, a beamforming technique may be used to compensatefor path loss. Beamforming technique focuses the RF energy into a narrowdirection to allow the RF beam to propagate farther in that direction.Using the beamforming technique, non-line of sight (NLOS) RFcommunication in the millimeter wavelength spectrum may rely onreflection and/or diffraction of the beams to reach the UE. If thedirection becomes blocked, either because of UE movement or changes inthe environment (e.g., obstacles, humidity, rain, etc.), the beam maynot be able to reach the UE. Thus, in order to ensure that the UE hascontinuous, seamless coverage, multiple beams in as many differentdirection as possible may be available. In an aspect, the beamformingtechnique may require that the mmW base stations and the UEs transmitand receive in a direction that allows the most RF energy to becollected.

The base station 502 may include hardware for performing analog and/ordigital beamforming. If the base station 502 is equipped with analogbeamforming, at any one time, the base station 502 may transmit orreceive a signal in only one direction. If the base station 502 isequipped with digital beamforming, the base station 502 may concurrentlytransmit multiple signals in multiple directions or may receive multiplesignals concurrently in multiple directions.

Further, the UE 504, for example, may include hardware for performinganalog and/or digital beamforming. If the UE 504 is equipped with analogbeamforming, at any one time, the UE 504 may transmit or receive asignal in only one direction. If the UE 504 is equipped with digitalbeamforming, the UE 504 may concurrently transmit multiple signals inmultiple directions or may concurrently receive multiple signals inmultiple directions.

In the mmW network, UEs may perform beam sweeps with mmW base stationswithin range. For example, the base station 502 may transmit m beams ina plurality of different spatial directions. The UE 504 may listen/scanfor the beam transmissions from the base station 502 in n differentreceive spatial directions. When listening/scanning for the beamtransmissions, the UE 504 may listen/scan for the beam sweeptransmission from the base station 502 m times in each of the ndifferent receive spatial directions (a total of m*n scans). In anotheraspect, in a beam sweep, the UE 504 may transmit n beams in a pluralityof different spatial directions. The base station 502 listens/scans forthe beam transmissions from the UE 504 in m different receive spatialdirections. When listening/scanning for the beam transmissions, the basestation 502 may listen/scan for the beam sweep transmission from the UE504 n times in each of the m different receive spatial directions (atotal of m*n scans).

Based on the performed beam sweeps, the UEs and/or the mmW base stationsmay determine a channel quality associated with the performed beamsweeps. For example, the UE 504 may determine the channel qualityassociated with the performed beam sweeps. Alternatively, the basestation 502 may determine the channel quality associated with theperformed beam sweeps. If the UE 504 determines a channel qualityassociated with the performed beam sweeps, the UE 504 may send thechannel quality information (also referred to as beam sweep resultinformation) to the base station 502. The UE 504 may send the beam sweepresult information to the base station 502. If the base station 502determines a channel quality associated with the performed beam sweeps,the base station 502 may send the beam sweep result information to theUE 504. In an aspect, the channel quality may be affected by a varietyof factors. The factors include movement of the UE 504 along a path ordue to rotation (e.g., a user holding and/or rotating the UE 504),movement along a path behind obstacles, and/or movement withinparticular environmental conditions (e.g., obstacles, rain, humidity).The UE 504 and the base station 502 may also exchange other information,for example, associated with for beamforming (e.g., analog or digitalbeamforming capabilities, beamforming type, timing information,configuration information, etc.).

Based on the received information, the base station 502 and/or the UE504 may determine various configuration information, such as mmW networkaccess configuration information, information for adjusting beamsweeping periodicity, information regarding overlapping coverage forpredicting a handoff to another base station, such as a mmW basestation.

In an aspect, a beam set may contain eight different beams. For example,FIG. 5A illustrates eight beams 521, 522, 523, 524, 525, 526, 527, 528for eight directions. In aspects, the base station 502 may be configuredto beamform for transmission of at least one of the beams 521, 522, 523,524, 525, 526, 527, 528 toward the UE 504. In one aspect, the basestation 502 can sweep/transmit directions using eight ports during asubframe (e.g., synchronization subframe).

In an aspect, a base station may transmit a signal, such as a beamreference signal (BRS), in a plurality of directions, for example,during a synchronization subframe. In one aspect, this transmission maybe cell-specific. Referring to FIG. 5B, the base station 502 maytransmit a first set of beams 521, 523, 525, 527 in four directions. Forexample, the base station 502 may transmit a BRS in a synchronizationsubframe of each of the transmit beams 521, 523, 525, 527.

In an aspect, these beams 521, 523, 525, 527 transmitted in the fourdirections may be odd-indexed beams 521, 523, 525, 527 for the fourdirections out of a possible eight for the beam set. For example, thebase station 502 may be capable of transmitting beams 521, 523, 525, 527in directions adjacent to other beams 522, 524, 526, 528 that the basestation 502 is configured to transmit. In an aspect, this configurationin which the base station 502 transmits beams 521, 523, 525, 527 for thefour directions may be considered a “coarse” beam set.

The UE 504 may determine a respective beam index (sometimes abbreviatedas “BI”) corresponding to a respective beam. In various aspects, thebeam index may be indicate at least a direction for communicatingthrough a corresponding beam toward the UE 504 (e.g., a beamformingdirection). For example, the beam index may be a logical beam indexassociated with an antenna port, OFDM symbol index, and/or BRStransmission period, which may be indicated by one or more bits (e.g., 9bits). For example, the UE 504 may be configured to determine a beamindex corresponding to a beam based on a time at which a BRS isreceived—e.g., a symbol or slot during which a BRS is received mayindicate a beam index corresponding to a beam.

In FIG. 5C, the UE 504 may determine or select a beam index (sometimesabbreviated as “BI”) that is strongest or preferable. For example, theUE 504 may determine that the beam 525 carrying a BRS is strongest orpreferable. The UE 504 may select a beam by measuring values for areceived power or received quality associated with each of the first setof beams 521, 523, 525, 527. In one aspect, the received power may bereferred to as a BRS received power (BRSRP).

The UE 504 may compare respective values to one another. The UE 504 mayselect a “best” beam. In an aspect, the best beam may be a beam thatcorresponds to the greatest or highest value (e.g., the best beam may bea beam with the highest BRSRP). The selected beam may correspond to abeam index, which may be a beam index with respect to the base station502. For example, the UE 504 may determine that the BRSRP correspondingto the fifth beam 525 is the highest, and therefore the fifth beam 525is the best beam as determined by the UE 504.

The UE 504 may transmit a first indication 560 of the fifth beam 525 tothe base station 502. In an aspect, the first indication 560 may includea request to transmit a beam refinement reference signal (BRRS). TheBRRS may be UE-specific. One of ordinary skill would appreciate that theBRRS may be referred to by different terminology without departing fromthe present disclosure, such as a beam refinement signal, a beamtracking signal, or another term.

In one aspect, the base station 502 may trigger transmission of thefirst indication 560. For example, the base station 502 may triggertransmission of the first indication 560 by a DCI message.

The base station 502 may receive the first indication 560. In oneaspect, the first indication 560 may include a beam adjustment request(BAR). (e.g., a request for beam tracking, a request for a BRRS, arequest for the base station to start transmitting on an indicated beamindex without any further beam tracking, and the like). In one aspect,the first indication 560 may be indicated by a scheduling request. Basedon the first indication 560, the base station 502 may determine the beamindex corresponding to the fifth beam 525.

In FIG. 5D, the base station 502 may transmit a second set of beamsbased on the first indication 560 (e.g., based on a beam index indicatedby the first indication 560). For example, the UE 504 may indicate thata fifth beam 525 is the best beam and, in response, the base station 502may transmit a second set of beams 524, 525, 526 to the UE 504 based onthe indicated beam index. In an aspect, the beams 524, 525, 526transmitted based on the first indication 560 may be closer (e.g.,spatially and/or directionally) to the fifth beam 525 than those otherbeams 521, 523, 527 of the first set of beams.

In an aspect, the beams 524, 525, 526 transmitted based on the firstindication 560 may be considered a “fine” beam set. In an aspect, thebase station 502 may transmit a BRRS through each of the beams 524, 525,526 of the fine beam set. In an aspect, the beams 524, 525, 526 of thefine beam set may be adjacent. In an aspect, BRRS transmission can span1, 2, 5 or 10 OFDM symbols and may be associated with a BRRS resourceallocation, BRRS process indication, and/or a beam refinement processconfiguration.

Based on the BRRS transmission through the beams 524, 525, 526 of thefine beam set, the UE 504 may transmit a second indication 565 to thebase station 502 to indicate a “best” beam. In an aspect, the secondindication 565 may use two (2) bits to indicate the selected beam. Forexample, the UE 504 may transmit the second indication 565 thatindicates a beam index corresponding to the selected beam 525. In oneaspect, the second indication 565 may report beam refinement information(BRI). In one aspect, the second indication 565 may include a resourceindex (e.g., a BRRS-RI) and/or a reference power (RP) associated withthe reception of the BRRS as measured by the UE 504 (e.g., a BRRS-RP).The base station 502 may then communicate with the UE 504 through theselected beam 525.

Referring to FIG. 5E, the base station 502 may transmit a BRS in aplurality of directions during a synchronization subframe. In an aspect,the base station 502 may transmit the BRS continuously, e.g., even afterthe UE 504 has communicated the second indication 565. For example, thebase station 502 may transmit beams 521, 523, 525, 527 that each includea BRS (e.g., a “coarse” beam set).

Referring to FIG. 5F, the quality of a selected beam 525 may deteriorateso that the UE 504. For example, when the base station 502 and the UE504 are communicating through the selected beam 525, the selected beam525 may become occluded or otherwise unsatisfactory such that the basestation 502 and the UE 504 may prefer to communicate through anotherbeam. Based on the BRS (e.g., transmitted during a synchronizationsubframe), the UE 504 may determine a new beam 523 through which tocommunicate. For example, the UE 504 may determine that the third beam523 through which a BRS is communicated may be the best beam. The UE 504may select a beam based by measuring values for a received power (e.g.,BRSRP) or received quality associated with each of the set of beams 521,523, 525, 527, comparing respective values to one another, and selectingthe beam that corresponds to the highest value. The selected beam maycorrespond to a beam index at the base station 502. The UE 504 maytransmit a third indication 570 indicating this beam index to the basestation 502. In an aspect, the third indication 570 may include arequest to transmit a BRRS. The BRRS may be UE-specific. In one aspect,a BAR may be used to request the base station 502 to transmit a BRRS. Inone aspect, the third indication 570 may be triggered by the basestation 502, such as by a DCI message. Similar to the first indication560, the third indication 570 may be included in a scheduling request.

With respect to FIG. 5G, the base station 502 may receive the thirdindication 570 from the UE 504. The base station 502 may be configuredto determine a beam index based on at least the third indication 570.The base station 502 and the UE 504 may perform a beam refinementprocedure, such as illustrated with respect to FIG. 5E (e.g., in orderto select a new beam through which to communicate).

Referring to FIG. 6, a diagram of a wireless communications system 600is illustrated. The base station 602 may be an aspect of the basestation 502, the base station 310, the base station 102, the mmW basestation 180, and/or another base station. The UE 604 may be an aspect ofthe UE 504, the UE 350, the UE 104, the UE 182, and/or another UE.

In the illustrated aspect, the base station 602 may include up to 8antenna ports for BRS transmission. In various aspects, the base station602 may send, to the UE 604, one or more BRSs 612 a-h (e.g., asdescribed with respect to FIGS. 5A-5G). Each BRS 612 a-h may becommunicated through a respective beam 620 a-h. For example, the basestation 602 may send a first BRS 612 a through the first beam 620 a withwhich the first BRS 612 a is associated. The UE 604 may track one ormore beams 620 a-h through periodically measuring a BRS 612 a-hassociated with a respective one of the beams 620 a-h. In an aspect, thetransmission period of the BRSs 612 a-h may be configured by anindicator on a physical broadcast channel (PBCH), such as an enhanced orevolved PBCH (ePBCH). The transmission period may be associated with thetime to sweep the beams 620 a-h through which the BRS 612 a-h istransmitted.

In aspects, the UE 604 may receive, through the set of beams 620 a-h, aset of BRSs 612 a-h. Each BRS 612 a-h may be associated with a beamindex that corresponds to the beam 620 a-h through which the BRS 612 a-his sent. The UE 604 may measure a signal quality of each BRS 612 a-h,and each measured signal quality may correspond to a beam 620 a-h of theset of beams. For example, the UE 604 may measure the signal qualitiesof the third BRS 612 c, the fourth BRS 612 d, the fifth BRS 612 e, andthe sixth BRS 612 f, which respectively correspond to the third beam 620c, the fourth beam 620 d, the fifth beam 620 e, and the sixth beam 620f. In aspects, the UE 604 may not receive each of the BRSs 612 a-h.

In one aspect, the UE 604 may measure the signal quality as a receivedpower. In one aspect, the signal quality may correspond to a BRSRP. Forexample, the UE 604 may measure the BRSRP in decibels (dB) and/ordecibel-milliwatts (dBm). In other aspects, the UE 604 may measure thesignal quality as another value, such as a received quality (RQ) (e.g.,a BRSRQ), an signal-to-interference ratio (SIR), asignal-to-interference-plus-noise ratio (SINR), a reference signalreceived power (RSRP), a reference signal received quality (RSRQ), areceived signal strength indicator (RSSI), or another metric.

In an aspect, the UE 604 may maintain a set of candidate beam indexes630 corresponding to a set of the best measured signal qualities forBRSs 612 a-h received through the beams 620 a-h. For example, the bestmeasured signal qualities may correspond to the highest measured signalqualities. The number N of candidate beam indexes in the set ofcandidate beam indexes 630 may be predetermined (e.g., N may equal 4).In an aspect, the UE 604 may record a null value when the UE 604 isunable to measure signal qualities of N beams. For example, if N equalsfour and the UE 604 is unable to measure a fourth signal quality, the UE604 may record a null value in the set of candidate beam indexes 630.

In an aspect, the UE 604 may maintain the set of candidate beam indexes630 based on a most recent set of signal qualities measured for the setof BRSs 612 a-h. That is, the set of candidate beam indexes 630 may bethe correspond to the measured signal qualities for each of the BRSs 612a-h that is most recently received by the UE 604.

In another aspect, the UE 604 may maintain the set of candidate beamindexes 630 based on a time-averaged set of signal qualities of the setof BRSs 612 a-h. For example, the UE 604 may receive a plurality of setsof the BRSs 612 a-h, which may be periodically transmitted by the basestation 602. The UE 604 may average a respective signal qualitiesmeasured for each BRS of the set of BRSs 612 a-h—e.g., the UE 604 mayaverage the most recent three or four measured signal qualities for thefirst BRS 612 a, the UE 604 may average the most recent three or fourmeasured signal qualities for the second BRS 612 b, and so forth. The UE604 may maintain the set of candidate beam indexes 630 based on thetime-averaged set of signal qualities of BRSs.

In another aspect, the UE 604 may maintain the set of candidate beamindexes 630 based on a filtered set of signal qualities of BRSs 612 a-h.For example, the UE 604 may apply a filter during or after measuring thesignal qualities for the BRSs 612 a-h in order to determine the best orhighest signal qualities corresponding to the best or highest BRSs ofthe set of BRSs 612 a-h.

In one aspect, the UE 604 may maintain the set of candidate beam indexes630 based on one or more other criteria, which may be received (e.g.,from the base station 602) and/or determined by the UE 604. In oneaspect, the UE 604 may maintain the set of candidate beam indexes 630based on an indication of one or more beams to include or exclude fromthe maintained set of candidates beam indexes 630. The indication of oneor more beams to include or exclude may be received from the basestation 602, and may include one or more beam indexes. According toaspects, the UE 604 may then include or exclude indicated beam indexesfrom the set of candidate beam indexes 630.

In another aspect, the UE 604 may maintain the set of candidate beamindexes 630 based on one or more hysteresis criteria for including abeam index in or excluding a beam index from the set of candidate beamindexes 630. The hysteresis criteria may include, for example, inclusionin or exclusion from the set of candidate beam indexes 630 if a measuredsignal quality deviates from a predetermined value (e.g., apredetermined threshold) or deviates from another signal qualitymeasured for another BRS of the set of BRSs 612 a-h. In another aspect,the hysteresis criteria may include inclusion or exclusion from the setof candidate beam indexes 630 if a predetermined number of values (e.g.,BRSRPs) measured for a BRSs of a beam fall below (e.g., for exclusion)or exceed (e.g., for inclusion) a predetermined threshold. For example,if the 3 most recent BRSRPs measured for the third BRSs 612 c fall belowa threshold value, then the beam index corresponding to the third beam620 c may be excluded from the candidate beam set 630 (although the beamindex corresponding to the third beam 620 c would not be excluded ifonly one BRSRP measured for the BRSs 612 c falls below the thresholdvalue).

According to various aspects, the UE 604 may transmit, to the basestation 602, a beam state information (BSI) report 642 indicating atleast one beam index. In an aspect, the BSI report 642 may be a BSIreport that includes a beam index and a corresponding measured signalquality (e.g., the BRSRP measured for a BRS 612 a-h received through abeam 620). For example, the UE 604 may select a beam index andcorresponding signal quality from the maintained set of candidate beamindexes 630, and transmit the selected beam index and correspondingsignal quality in the BSI report 642. In an aspect, the UE 604 maytransmit the BSI report 642 in response to a request 640 received fromthe base station 602.

In an aspect, the BSI report 642 may be carried on a PUCCH or a PUSCH.For example, the UE 604 may send, to the base station 602, the BSIreport 642 on a PUCCH (e.g., an enhanced PUCCH) or a PUSCH (e.g., anenhanced PUSCH).

Referring to FIG. 7, a diagram of a wireless communications system 700is illustrated. The base station 702 may be an aspect of the basestation 602, the base station 502, the base station 310, the basestation 102, the mmW base station 180, and/or another base station. TheUE 704 may be an aspect of the UE 604, the UE 504, the UE 350, the UE104, the UE 182, and/or another UE.

In the illustrated aspect, the base station 702 may include up to 8antenna ports for BRS transmission. In various aspects, the base station702 may send, to the UE 704, one or more BRSs 712 a-h (e.g., asdescribed with respect to FIGS. 5A-5G and/or FIG. 6). Each BRS 712 a-hmay be communicated through a respective beam 720 a-h. For example, thebase station 702 may send a first BRS 712 a through the first beam 720 awith which the first BRS 712 a is associated. The UE 704 may track oneor more beams 720 a-h through periodically measuring a BRS 712 a-hassociated with a respective one of the beams 720 a-h. In an aspect, thetransmission period of the BRSs 712 a-h may be configured by anindicator on a PBCH, such as an ePBCH. The transmission period may beassociated with the time to sweep the beams 720 a-h through which theBRS 712 a-h is transmitted.

In aspects, the base station 702 may transmit a set of beams 720 a-h.According to various aspects, the base station 702 may communicate withthe UE 704 through a first serving beam 720 e. The first serving beam720 e may correspond to a beam index.

In one aspect, the base station 702 and the UE 704 may communicatethrough the first serving beam 720 e for uplink communication and/ordownlink communication. In an aspect, the base station 702 and the UE704 may use the first serving beam 720 e for one of uplink communicationor downlink communication, but may use a different beam (e.g., thefourth beam 720 d) for the other of uplink communication or downlinkcommunication (e.g., in aspects in which uplink/downlink reciprocitydoes not work or where the base station 702 is intended to serve the UE704 on certain beams).

The base station 702 and the UE 704 may be configured to switch beams.In an aspect, the base station 702 may initiate the beam switching. Forexample, the base station 702 may set up a beam 720 a-h for a channelfor which a beam 720 a-h is not configured. In another example, the basestation 702 and/or the UE 704 may select a different beam 720 a-h inorder to provide a better connection for communication on a channelbetween the base station 702 and the UE 704. In one aspect, the basestation 702 and the UE 704 may modify and/or set up a beam for uplinkcommunication, downlink communication, or both uplink and downlinkcommunication.

In an aspect, the base station 702 may send, to the UE 704, a command710 associated with beam modification (e.g., a beam modification commandor another signal). In one aspect, the base station 702 may include thecommand 710 in a MAC CE. In another aspect, the base station 702 mayinclude the command 710 in a DCI message. In another aspect, the basestation 702 may send the command 710 to the UE 704 via RRC signaling.

The base station 702 may select a beam 720 a-h to which to switch forcommunication between the base station 702 and the UE 704. For example,the base station 702 may determine that communication with the UE 704 isto continue through the fourth beam 720 d. The base station 702 maydetermine a beam index corresponding to the selected fourth beam 720 d.The base station 702 may generate a command 710 that is to indicate atleast one beam index for communicating through the selected fourth beam720 d on at least one channel. The base station 702 may send, to the UE704, the command 710 in order to switch the serving beam from thecurrent serving beam 720 e to the selected fourth beam 720 d.

In various aspects, the base station 702 may determine a channel forwhich the command 710 is applicable. For example, the base station 702may determine a beam modification command for an individual channel orfor a group of channels. In one aspect, the base station 702 mayindicate, via the command 710, at least one channel to which the command710 is applicable. That is, the base station 702 may indicate, by thecommand 710, a channel corresponding to a beam index indicated by thecommand 710. In an aspect, the command 710 may indicate a group ofchannels that includes the at least one channel determined by the basestation 702.

In one aspect, the command 710 may indicate a channel (or group ofchannels) by a format. For example, the base station 702 may send thecommand 710 as a DCI message and the format of the DCI message mayindicate a channel (or group of channels) to which at least one beamindex indicated by the command 710 is applicable. According to anotherexample, the command 710 may indicate a channel (or group of channels)based on inclusion of the command 710 in a MAC CE by the base station702. For example, inclusion of the command 710 in a MAC CE may indicate,to the UE 704, that the UE 704 is to switch to the beam index indicatedby the command 710 for PDCCH, PDSCH, CSI-RS, PUCCH, PUSCH, and/or SRS.

According to an aspect, the base station 702 may generate the command710 to indicate a plurality of beam indexes. In one aspect, the basestation 702 may generate the command 710 to indicate one or morechannels. In one aspect, the base station 702 may generate the command710 to indicate a corresponding channel(s) to which each beam index ofthe plurality of beam indexes is applicable. That is, the base station702 may generate the command 710 to indicate a plurality of beam indexesand a plurality of channels, and the command 710 may indicate acorresponding channel (or channel group) for each beam index of theplurality of beam indexes.

According to one example, the base station 702 may determine that thecurrent serving beam 720 e should be modified for channel stateinformation reference signals (CSI-RS) and/or BRRS, but the otherdownlink and/or uplink beams 720 a-h should remain unchanged. Forexample, the base station 702 may continue communication through thecurrent serving beam 720 e for other channels other than the CSI-RSand/or BRRS, and switch to the selected fourth beam 720 d forcommunication carried on the CSI-RS and/or BRRS.

In another example, the base station 702 may determine that at least onebeam through which the PDCCH and/or PDSCH are communicated should beswitched to at least the selected fourth beam 720 d, but continue uplinkcommunication through at least the current serving beam 720 e.

In a third example, the base station 702 may determine that the currentserving beam 720 e is to be changed to the selected fourth beam 720 dfor uplink communication (e.g., including PUSCH, PUCCH, and SRSchannels), but continue with the current serving beam 720 e for downlinkcommunication (e.g., including PDSCH, PDCCH, CSI-RS, and BRRS), forexample, when reciprocity cannot be assumed and/or to provide schedulingand/or multiplexing flexibility for the base station 702.

While the present disclosure illustrates communication on one beam(e.g., the current serving beam 720 e and the selected fourth beam 720d), it will be appreciated that communication on channels may occurthrough more than one beam.

The UE 704 may receive, from the base station 702, the command 710. Inresponse to the command 710, the UE 704 communicate on at least onechannel with the base station 702 through the at least one beamcorresponding to the at least one beam index indicated by the command710. For example, the UE 704 may switch the current serving beam 720 eat the UE 704 to the selected fourth beam 720 d after receiving thecommand 710. Accordingly, the UE 704 may communicate with the basestation 702 through the selected fourth beam 720 d.

In one aspect, the UE 704 may switch beams at a determined time, whichmay correspond to a symbol or a subframe. The UE 704 may determine thetime (e.g., subframe) based on the command 710. For example, when thebase station 702 includes the command 710 in a MAC CE, the UE 704 maydetermine to switch communication through the current serving beam 720 eto the selected fourth beam 720 d at the beginning of a subframen+k_(beamswitch-delay-mac), where n is the subframe used for HARQ-ACKtransmission associated with the MAC CE and k_(beamswitch-delay-mac) isequal to 14.

According to another example, the UE 704 may receive the command 710 ina DCI message. In response to receiving the command 710 in a DI message,the UE 704 may switch from the current serving beam 720 e to theselected fourth beam 720 d at the beginning of a subframen+k_(beamswitch-delay-dic), where n is the subframe used fortransmission of a BSI report (e.g., the BSI report 642) andk_(beamswitch-delay-dic) is equal to 11.

According to an aspect, the command 710 may include a request from thebase station 702 for a BSI report, such as the request 640. The requestfor a BSI report may be communicated via a DCI message. In such anaspect, the base station 702 may set a field (e.g., a beam switchindication field) of DCI message to a predetermined value, such as “1”to indicate that the UE 704 is to switch beams and “0” to indicate thatthe UE 704 is to continue communicating using the current serving beam720 e. When the base station 702 indicates the command 710 by setting afield of a DCI message to a predetermined value indicating a beam switchcommand, the UE 704 may determine that the UE 704 is to switch to thefirst beam indicated by a BSI report (e.g., the BSI report 642).

After switching from the current serving beam 720 e to the selectedfourth beam 720 d indicated by the command 710, the UE 704 and the basestation 702 may communicate on at least one channel through the selectedfourth beam 720 d. Accordingly, the beam index corresponding to theselected fourth beam 720 d for communication by the UE 704 may match thebeam index corresponding to the selected fourth beam 720 d forcommunication by the base station 702.

With reference to FIG. 8, a diagram of a wireless communications system800 is illustrated. The base station 802 may be an aspect of the basestation 702, the base station 602, the base station 502, the basestation 310, the base station 102, the mmW base station 180, and/oranother base station. The UE 804 may be an aspect of the UE 704, the UE604, the UE 504, the UE 350, the UE 104, the UE 182, and/or another UE.

In the illustrated aspect, the base station 802 may include up to 8antenna ports for BRS transmission. In various aspects, the base station802 may send, to the UE 804, one or more BRSs 812 a-h (e.g., asdescribed with respect to FIGS. 5A-5G, FIG. 6, and/or FIG. 7). Each BRS812 a-h may be communicated through a respective beam 820 a-h. Forexample, the base station 802 may send a first BRS 812 a through thefirst beam 820 a with which the first BRS 812 a is associated. The UE804 may track one or more beams 820 a-h through periodically measuring aBRS 812 a-h associated with a respective one of the beams 820 a-h. In anaspect, the transmission period of the BRSs 812 a-h may be configured byan indicator on a PBCH, such as an ePBCH. The transmission period may beassociated with the time to sweep the beams 820 a-h through which theBRS 812 a-h is transmitted.

In aspects, the UE 804 may receive, through the set of beams 820 a-h, aset of BRSs 812 a-h. Each BRS 812 a-h may correspond to a beam indexthat corresponds to the beam 820 a-h through which the BRS 812 a-h issent. The UE 804 may measure a signal quality of each BRS 812 a-h, andeach measured signal quality may correspond to a beam 820 a-h of the setof beams. For example, the UE 804 may measure the signal qualities ofthe third BRS 812 c, the fourth BRS 812 d, the fifth BRS 812 e, and thesixth BRS 812 f, which respectively correspond to the third beam 820 c,the fourth beam 820 d, the fifth beam 820 e, and the sixth beam 820 f.In aspects, the UE 804 may not receive each of the BRSs 812 a-h.

In one aspect, the UE 804 may measure the signal quality by determininga received power. In one aspect, the signal quality may correspond to aBRSRP. For example, the UE 804 may measure the BRSRP in dB and/or dBm.In other aspects, the UE 804 may measure the signal quality as anothervalue, such as a RQ, an SIR, a SINR, a RSRP, a RSRQ, a RSSI, or anothermetric.

In an aspect, the UE 804 may maintain a set of candidate beam indexes830 corresponding to a set of the best measured signal qualities forBRSs 812 a-h received through the beams 820 a-h. For example, the bestmeasured signal qualities may correspond to the highest determinedreceived powers (e.g., the highest determined BRSRPs). The number N ofcandidate beam indexes in the set of candidate beam indexes 830 may bepredetermined (e.g., N may equal 4). In an aspect, the UE 804 may recorda null value when the UE 804 is unable to measure signal qualities of Nbeams. For example, if N equals four and the UE 804 is unable to measurea fourth signal quality, the UE 804 may record a null value in the setof candidate beam indexes 830. The UE may sort the set of candidate beamindexes 830 in decreasing order of BRSRP.

According to aspects, the base station 802 may determine a number of BSIreports that the UE 804 is to transmit to the base station 802. Forexample, the base station 802 may communicate with the UE 804 through asecond beam 820 b, which may be a serving beam. The base station 802 maydetermine that communication is to occur through a different beam and/orthat the base station 802 is to store information indicating alternative(e.g., candidate) beam(s) that may be used for communication with the UE804 in the future (e.g., in case a serving beam fails, a power and/orquality of a serving beam deteriorates, etc.). Accordingly, the basestation 802 may request that the UE 804 send BSI reports to the basestation 802.

The base station 802 may determine that zero, one, or more than one(e.g., two or four) BSI reports should be sent to the base station bythe UE 804. Therefore, the base station 802 may send, to the UE 804, amessage 840 indicating a number X of BSI reports (e.g., zero, one, two,or four) that are to be sent to the base station 802 by the UE 804.

In various aspects, the base station 802 may transmit, to the UE 804, amessage 840 requesting BSI reports. In one aspect, the message 840 maybe a two-bit message. In one aspect, the message 840 may be included inor indicated by a DCI message. The message 840 may be included in anuplink DCI message or a downlink DCI message. Further, the message 840may be one of a plurality of DCI formats. In another aspect, the message840 may be included in a random access response (RAR) message (e.g., theMSG2 412, an uplink grant, etc.). In another aspect, the base station802 may transmit, to the UE 804, the message 840 via RRC signaling(e.g., the base station 802 may transmit the message 840 as an RRCmessage).

According to various aspects, the UE 804 may transmit, to the basestation 802, a BSI report 842 indicating at least one beam index. In anaspect, the BSI report 842 may be a BSI report that includes a beamindex (e.g., a beam index 832) and a corresponding measured signalquality (e.g., the BRSRP 834 measured for a BRS 812 a-h received througha beam 820). In an aspect, the UE 804 may transmit the BSI report 842 inresponse to a message 840 (e.g., request) received from the base station802.

In the illustrated aspect, the UE 804 may determine a number N ofcandidate beam indexes (e.g., N may be equal to 4) based on determiningBRSRPs 834 for BRSs 812 a-h corresponding to beams 820 a-h. For example,the UE 804 may measure a third BRSRP 834 c for the third BRS 812 ccorresponding to the third beam 820 c, a fourth BRSRP 834 d for thefourth BRS 812 d corresponding to the fourth beam 820 d, a fifth BRSRP834 e for the fifth BRS 812 e corresponding to the fifth beam 820 e, anda sixth BRSRP 834 f for the sixth BRS 812 f corresponding to the sixthbeam 820 f.

The UE 804 may store the BRSRPs 834 c-f for the BRSs 812 c-f andrespective corresponding beam indexes 832 c-f in the set of candidatebeam indexes 830. The UE 804 may maintain the set of candidate beamindexes 830 by sorting the beam indexes 832 c-f based on thecorresponding BRSRPs 834 c-f For example, the beam indexes 832 c-f maybe sorted by the “best” (e.g., highest) corresponding BRSRPs 834 c-fFurther to such an example, the fifth BRSRP 834 e corresponding to thefifth beam index 832 e may be a highest BRSRP and, therefore, storedfirst in the set of candidate beam indexes 830. The sixth BRSRP 834 fcorresponding to the sixth beam index 832 f may be a second highestBRSRP and, therefore, stored second in the set of candidate beam indexes830, and so forth.

Based on the message 840 requesting BSI reports, the UE 804 maydetermine a number X of BSI reports 842 to send to the base station 802.Each BSI report 842 may include at least a beam index (e.g., a beamindex 832) and a received power (e.g., a BRSRP 834) associated with abeam 820 a-h through which a BRS 812 a-h is received.

According to aspects, the UE 804 may determine the number X of BSIreports 842 to send to the base station 802 based on the message 840requesting the BSI. In one aspect, the number X may be greater than orequal to zero, but less than or equal to the number N of candidate beamindexes maintained by the UE. In an aspect, the UE 804 may determine thenumber X based on the message 840 by determining the number X based on atype of the message 840. A type of message may be, for example, a DCImessage (e.g., a downlink DCI message), an RAR message (e.g., the MSG2412, an RAR grant, or another uplink grant, etc.), or another type ofmessage.

In one aspect, the UE 804 may determine that the number X of BSI reports842 to send to the base station 802 is one when the message 840 is a DCImessage (e.g., a downlink DCI message). For example, when the UE 804receives the message 840 in a downlink DCI message, the UE 804 maydetermine that one BSI report 842 is to be sent to the base station 802.

In one aspect, the base station 802 may include, in the message 840, anindication of a time and/or frequency resource for a channel that is tocarry the BSI report 842. Accordingly, the UE 804 may determine a timeand/or frequency resource for a channel that is to carry the BSI report842 based on the message 840.

In an aspect, the UE 804 may determine the channel that is to carry theBSI report 842 based on the message 840 (e.g., the type of the message840). For example, the UE 804 may determine that a PUCCH (e.g., anenhanced PUCCH (ePUCCH), xPUCCH, etc.) is to carry the BSI report 842when the message 840 is a DCI message (e.g., a downlink DCI message).

According to one aspect, the UE 804 may determine the number X of BSIreports to send based on the channel that is to carry the BSI reports842. For example, the UE 804 may determine that the UE 804 is to sendthe message on a PUCCH (e.g., based on the message 840). Accordingly,the UE 804 may determine that the UE 804 is to send one BSI report 842on the PUCCH based on the determination that the PUCCH is to carry theBSI report 842.

In an aspect, when the UE 804 determines that the UE 804 is to send oneBSI report, the UE 804 may send a BSI report that includes BSIindicating a beam index 832 corresponding to the highest BRSRP 834 inthe set of candidate beam indexes 830. For example, the UE 804 maydetermine that the fifth BRS 812 e received through the fifth beam 820 ehas a highest BRSRP 834 e. Therefore, the UE 804 may send one BSI report842 that includes the fifth beam index 832 e corresponding to the fifthbeam 820 e and further includes the fifth BRSRP 834 e corresponding tothe fifth beam index 832 e.

In another aspect, the UE 804 may determine that the number X of BSIreports 842 to send to the base station 802 is one or more when themessage 840 is an RAR message (e.g., the MSG2 412, an uplink grant,etc.). The RAR message may indicate an uplink grant. In another aspect,another uplink grant may be indicated through an uplink DCI message. Forexample, when the UE 804 receives the message 840 in an RAR message, theUE 804 may determine that one or more BSI reports 842 are to be sent tothe base station 802. In another example, when the UE 804 receives themessage 840 in an uplink DCI message, the UE 804 may determine that oneor more BSI reports 842 are to be sent to the base station 802.

In one aspect, the base station 802 may include, in the message 840, anindication of at least one time and/or frequency resource for a channelthat is to carry the BSI reports 842. For example, the UE 804 maytransmit a BSI report 842 on one or more uplink resources associatedwith a connection request message (e.g., the MSG3 414) granted through acontention-based RACH procedure (e.g., granted through an RAR or MSG2412). Accordingly, the UE 804 may determine at least one time and/orfrequency resource for a channel that is to carry the one or more BSIreports 842 based on the message 840.

In an aspect, the UE 804 may determine the channel that is to carry theone or more BSI reports 842 based on the message 840 (e.g., based on thetype of the message 840). For example, the UE 804 may determine that aPUSCH (e.g., an enhanced PUSCH (ePUSCH), xPUSCH, etc.) is to carry theBSI reports 842 when the message 840 is included in an RAR message(e.g., the MSG2 412 or an uplink grant, such as an uplink DCI message).

According to one aspect, the UE 804 may determine the number X of BSIreports to send based on the channel that is to carry the BSI reports842. For example, the UE 804 may determine that the UE 804 is to sendthe message on a PUSCH (e.g., based on the message 840). Accordingly,the UE 804 may determine that the UE 804 is to send more than one (e.g.,two) BSI reports 842 on the PUSCH based on the determination that thePUSCH is to carry the BSI reports 842.

In one aspect, the base station 802 may include, in the message 840, anindication of the number X of BSI reports 842 to be sent. For example,the UE 804 may determine whether to send one, two, or four BSI reports842 based on an indication of the number X included in the message 840.For example, when the message 840 is included in an uplink DCI message,the uplink DCI message may indicate that zero, two, or four BSI reportsare to be sent.

In an aspect, when the UE 804 determines the number X of BSI reports 842to send, the UE 804 may send X BSI reports 842 for the X beam indexes832 corresponding to the X highest BRSRPs 834 in the set of candidatebeam indexes 830. For example, the UE 804 may determine, based on themessage 840, that four BSI reports 842 are requested by the base station802. Accordingly, the UE 804 may determine that the fifth BRS 812 ereceived through the fifth beam 820 e has a highest BRSRP 834 e, thesixth BRS 812 f received through the sixth beam 820 f has a secondhighest BRSRP 834 f, the fourth BRS 812 d received through the fourthbeam 820 d has a third highest BRSRP 834 d, and the third BRS 812 creceived through the third beam 820 c has a fourth highest BRSRP 834 c.Therefore, the UE 804 may send four BSI reports 842: a first of whichmay include the fifth beam index 832 e and the fifth BRSRP 834 e, asecond of which may include the sixth beam index 832 f and the sixthBRSRP 834 f, a third of which may include the fourth beam index 832 dand the fourth BRSRP 834 d, and a fourth of which may include the thirdbeam index 832 c and the third BRSRP 834 c. In an aspect, the BSIreports 842 may be sorted in decreasing order of BRSRP 834.

The base station 802 may receive the one or more BSI reports 842. Basedon the BSI reports 842, the base station 802 may select a beam 820 a-hwith which to communicate with the UE 804. For example, the base station802 may select the fifth beam 820 e corresponding to the fifth beamindex 832 e having the highest BRSRP 834 e, as indicated by at least oneBSI report 842. In an aspect, the base station 802 may select anotherbeam (e.g., the sixth beam 820 f) based on the BSI reports 842, forexample, if communication through the selected beam (e.g., the fifthbeam 820 e) fails.

Turning to FIG. 9, a diagram of a wireless communications system 900 isillustrated. The base station 902 may be an aspect of the base station802, the base station 702, the base station 602, the base station 502,the base station 310, the base station 102, the mmW base station 180,and/or another base station. The UE 904 may be an aspect of the UE 804,the UE 704, the UE 604, the UE 504, the UE 350, the UE 104, the UE 182,and/or another UE.

In the illustrated aspect, the base station 902 may include up to 8antenna ports for BRS transmission. In various aspects, the base station902 may send, to the UE 904, one or more BRSs 912 a-h (e.g., asdescribed with respect to FIGS. 5A-5G, FIG. 6, FIG. 7, and/or FIG. 8).Each BRS 912 a-h may be communicated through a respective beam 920 a-h.For example, the base station 902 may send a first BRS 912 a through thefirst beam 920 a with which the first BRS 912 a is associated. The UE904 may track one or more beams 920 a-h through periodically measuring aBRS 912 a-h associated with a respective one of the beams 920 a-h. In anaspect, the transmission period of the BRSs 912 a-h may be configured byan indicator on a PBCH, such as an ePBCH. The transmission period may beassociated with the time to sweep the beams 920 a-h through which theBRS 912 a-h is transmitted.

In aspects, the UE 904 may receive, through the set of beams 920 a-h, aset of BRSs 912 a-h. Each BRS 912 a-h may correspond to a beam indexthat corresponds to the beam 920 a-h through which the BRS 912 a-h issent. The UE 904 may measure a signal quality of each BRS 912 a-h, andeach measured signal quality may correspond to a beam 920 a-h of the setof beams. For example, the UE 904 may measure the signal qualities ofthe third BRS 912 c, the fourth BRS 912 d, the fifth BRS 912 e, and thesixth BRS 912 f, which respectively correspond to the third beam 920 c,the fourth beam 920 d, the fifth beam 920 e, and the sixth beam 920 f.In aspects, the UE 904 may not receive each of the BRSs 912 a-h.

In one aspect, the UE 904 may measure the signal quality by determininga received power. In one aspect, the signal quality may correspond to aBRSRP. For example, the UE 904 may measure the BRSRP in dB and/or dBm.In other aspects, the UE 904 may measure the signal quality as anothervalue, such as a RQ, an SIR, a SINR, a RSRP, a RSRQ, a RSSI, or anothermetric.

In an aspect, the UE 904 may select a beam 920 a-h for communicationwith the base station 902. For example, the UE 904 may select the fifthbeam 920 e. The UE 904 may select this fifth beam 920 e for one or bothof uplink and/or downlink communication. The UE 904 may select the fifthbeam 920 e based on a signal quality measured for the fifth BRS 912 eand/or based on resource information (e.g., time and/or frequencyresource information, which may be broadcast by the base station 902 assystem information). The UE 904 may select the fifth beam 920 e becausethe UE 904 may anticipate or estimate that the base station 902 maycommunicate with the UE 904 through the fifth beam 920 e, for example,based on the signal quality measured for the fifth BRS 912 ecorresponding to the fifth beam 920 e and/or resource information (e.g.,time and/or frequency resource information, which may indicate a time(e.g., subframe) and/or frequency).

The UE 904 may attempt a RACH procedure (e.g., the first RACH procedure940, the second RACH procedure 942, etc.). A RACH procedure may includevarious operations described with respect to FIG. 4A or 4B. For example,the UE 904 may attempt a RACH procedure (e.g., a contention-based RACHprocedure) by transmitting one or more RACH messages, such as a randomaccess preamble (e.g., the MSG1 410). The UE 904 may be still attemptingthe RACH procedure when transmitting another RACH message, such as aconnection request (e.g., the MSG3 414) in response to an RAR (e.g., theMSG2 412).

The UE 904 may determine the attempted RACH procedure has failed whenthe UE 904 fails to receive and/or decode a contention resolutionmessage (e.g., the MSG4 416) during the attempted RACH procedure. Byextension, the UE 904 would determine that an attempted RACH procedurehas failed when the UE 904 fails to receive an RAR (e.g., the MSG2 412)because the UE 904 would neither send a connection request (e.g., theMSG 413) nor receive a contention resolution message (e.g., the MSG4416) during the attempted RACH procedure. In an aspect, the UE 904 maydetermine a RACH procedure is successfully completed when the UE 904receives a contention resolution message (e.g., the MSG4 416), when theUE acquires a cell RNTI (C-RNTI) (e.g., based on the contentionresolution message), when the UE 904 receives and decodes an RRCconnection setup message, and/or when the UE 904 is synchronized withthe network after the RACH procedure.

In an aspect, the UE 904 may attempt a first RACH procedure 940 with thebase station 902 through the selected fifth beam 920 e. For example, theUE 904 may send a random access preamble (e.g., the MSG1 410) throughthe selected fifth beam 920 e. However, the UE 904 may determine thatthe first RACH procedure 940 has failed. For example, the UE 904 mayfail to receive an RAR (e.g., the MSG2 412) or a contention resolutionmessage (e.g., the MSG4 416).

Based on the attempted first RACH procedure 940, the UE 904 maydetermine information indicating that the first RACH procedure 940failed. The UE 904 may store this determined information. In one aspect,the information indicating that the first RACH procedure 940 failed mayinclude information associated with the selected fifth beam 920 e, suchas a beam index corresponding to the selected fifth beam 920 e and/or asignal quality (e.g., a BRSRP) measured for the fifth BRS 912 e receivedthrough the fifth beam 920 e. In another aspect, the informationindicating that the first RACH procedure 940 failed may include anindication of a subframe and/or symbol (e.g., a subframe index and/or asymbol index) during which a RACH message (e.g., a random accesspreamble or the MSG1 410) is sent through the selected fifth beam 920 e.

According to aspects, the UE 904 may attempt a second RACH procedure 942after the determination that the first RACH procedure 940 has failed.The UE 904 may determine that the second RACH procedure 942 issuccessful. For example, the UE 904 may successfully send a randomaccess preamble (e.g., the MSG1 410) to the base station 402. The UE 904may then successfully receive an RAR (e.g., the MSG2 412) from the basestation 402 based on the random access preamble. The UE 904 may thensuccessfully send a connection request message (e.g., the MSG3 414) tothe base station 402 based on the RAR. The UE 904 may then successfullyreceive a contention resolution message (e.g., the MSG4 416) from thebase station based on the connection request message. The UE 904 may besynchronized with a network that includes the base station 902 based onthe successful second RACH procedure 942.

In one aspect, the UE 904 may attempt the second RACH procedure 942 byincreasing a transmission power after the determination that the firstRACH procedure 940 failed. When the UE 904 performs the second RACHprocedure 942, the UE 904 may perform at least a portion of the secondRACH procedure 942 with the increased transmission power. For example,the UE 904 may send the random access preamble (e.g., the MSG1 410) withthe increased transmission power during the second RACH procedure 942.

In another aspect, the UE 904 may attempt the second RACH procedure 942by selecting a new beam for communication with the base station 902after the determination that the first RACH procedure 940 failed. Forexample, the UE 904 may select the sixth beam 920 f. In an aspect, theUE 904 may select the new sixth beam 920 f based on a signal qualitymeasured for the sixth BRS 912 f. In one aspect, the UE 904 may selectthe new sixth beam 920 f based on resource information (e.g., at leastone time and/or frequency resource, which may be broadcast by the basestation 902). The UE 904 may perform at least a portion of the secondRACH procedure 942 with the base station 902 through the new sixth beam920 f. For example, the UE 904 may send a random access preamble (e.g.,the MSG1 410) through the new sixth beam 920 f.

According to various aspects, the UE 904 may send, to the base station902, information 944 indicating that the first RACH procedure 940failed. The information 944 may include the information determined bythe UE 904, such as a beam index corresponding to the selected fifthbeam 920 e, a signal quality measured for the fifth BRS 912 e, asubframe index at which the UE 904 used the selected fifth beam 920 e, asymbol index at which the UE 904 used the selected fifth beam 920 e,etc.

In one aspect, the UE 904 may send the information 944 in a BSI report(e.g., a BSI report 842). The information 944 may indicate the beamindex corresponding to the selected fifth beam 920 e through which thefirst RACH procedure 940 failed. In the context of FIG. 8, the UE 904may send a BSI report 842 including the fifth beam index 832 ecorresponding to the selected fifth beam 820 e/920 e, and may send theinformation 944 indicating that the first RACH procedure 940 failedusing the selected fifth beam 820 e/920 e. For example, the base station902 may trigger BSI reporting by the UE 904 using a message 840 that isan RAR message received during the second RACH procedure 942. Inresponse, the UE 904 may sent a BSI report 842 that includes the fifthbeam index 832 e (and the fifth BRSRP 834 e), but may indicate that thefirst RACH procedure 940 failed using the selected fifth beam 820 e/920e corresponding to the fifth beam index 832 e.

According to an aspect, the UE 904 may exclude a beam indexcorresponding to the selected fifth beam 920 e from a set of candidatebeam indexes. In the context of FIG. 6, for example, the UE 904 mayexclude the fifth beam index corresponding to the fifth beam 620 e/920 efrom the set of candidate beam indexes 630. The UE 904 may includeanother beam index corresponding to another beam 920 a-h in the set ofcandidate beam indexes 630, for example, if a BRSRP is measured foranother BRS 912 a-h corresponding to another beam 920 a-h.

In various aspects, the base station 902 may receive the information 944indicating that the first RACH procedure 940 failed and may use thisinformation 944 for communication with the UE 904. In one aspect, thebase station 902 may schedule uplink or downlink communication with theUE 904 through different beams (e.g., the new sixth beam 920 f), forexample, when uplink/downlink reciprocity through one or more beams isunattainable for communication with the UE 904. For example, the basestation 902 may determine a different beam index corresponding to adifferent beam than the beam index associated with the failed RACHprocedure 940 for uplink or downlink communication with the UE 904. Inanother aspect, the base station 902 may exclude a beam index indicatedby the information 944 from a set of candidate beam indexes associatedwith uplink or downlink communication with the UE 904.

While FIG. 9 illustrates one failed RACH procedure 940, similaroperations may be performed when a plurality of RACH procedures fails.Accordingly, the UE 904 may send, to the base station 902, informationsimilar to the information 944 indicating that each RACH procedurefailed. For example, the UE 904 may send a respective beam index foreach beam used for each failed RACH procedure.

FIG. 10 illustrates an aspect of a wireless communications system 1000,according to various aspects. The base station 1002 may be an aspect ofthe base station 902, the base station 802, the base station 702, thebase station 602, the base station 502, the base station 310, the basestation 102, the mmW base station 180, and/or another base station. TheUE 1004 may be an aspect of the UE 904, UE 804, the UE 704, the UE 604,the UE 504, the UE 350, the UE 104, the UE 182, and/or another UE.

In the illustrated aspect, the base station 1002 may include up to 8antenna ports for BRS transmission. In various aspects, the base station1002 may send, to the UE 1004, one or more BRSs 1012 a-h (e.g., asdescribed with respect to FIGS. 5A-5G, FIG. 6, FIG. 7, and/or FIG. 8).Each BRS 1012 a-h may be communicated through a respective beam 1020a-h. For example, the base station 1002 may send a first BRS 1012 athrough the first beam 1020 a with which the first BRS 1012 a isassociated. The UE 1004 may track one or more beams 1020 a-h throughperiodically measuring a BRS 1012 a-h associated with a respective oneof the beams 1020 a-h. In an aspect, the transmission period of the BRSs1012 a-h may be configured by an indicator on a PBCH, such as an ePBCH.The transmission period may be associated with the time to sweep thebeams 1020 a-h through which the BRS 1012 a-h is transmitted.

In aspects, the UE 1004 may receive, through the set of beams 1020 a-h,a set of BRSs 1012 a-h. Each BRS 1012 a-h may be associated with a beamindex that corresponds to the beam 1020 a-h through which the BRS 1012a-h is sent. The UE 1004 may measure a signal quality of each BRS 1012a-h, and each measured signal quality may correspond to a beam 1020 a-hof the set of beams. For example, the UE 1004 may measure the signalqualities of the third BRS 1012 c, the fourth BRS 1012 d, the fifth BRS1012 e, and the sixth BRS 1012 f, which respectively correspond to thethird beam 1020 c, the fourth beam 1020 d, the fifth beam 1020 e, andthe sixth beam 1020 f. In aspects, the UE 1004 may not receive each ofthe BRSs 1012 a-h.

In one aspect, the UE 1004 may measure the signal quality by determininga received power. In one aspect, the signal quality may correspond to aBRSRP. For example, the UE 1004 may measure the BRSRP in dB and/or dBm.In other aspects, the UE 1004 may measure the signal quality as anothervalue, such as a RQ, an SIR, a SINR, a RSRP, a RSRQ, a RSSI, or anothermetric.

In an aspect, the UE 1004 may attempt a RACH procedure 1040 with thebase station 1002 through a fifth beam 1020 e. For example, the UE 1004may send a random access preamble (e.g., the MSG1 410) through the fifthbeam 1020 e, the base station 1002 may send an RAR (e.g., the MSG2 412)to the UE 1004 based on the random access preamble, and the UE 1004 maysend a connection request message (e.g., the MSG3 414) to the basestation 1002 based on the RAR.

The base station 1002 may determine that communication with the UE 1004is to occur through a serving beam of the beams 1020 a-h. For example,the base station 1002 may select the sixth beam 1020 f, which may bedifferent than the beam through which at least a portion of the RACHprocedure 1040 occurs. Therefore, the base station 1002 may determinethat the base station 1002 is to inform the UE 1004 of the beam indexcorresponding to sixth beam 1020 f, for example, by sending a beammodification command to the UE 1004.

The beam modification command may include at least a beam indexcorresponding to a respective one of the beams 1020 a-h. In variousaspects, the base station 1002 may include the beam modification commandin a contention resolution message 1042 (e.g., the MSG4 416), which maybe in response to a connection request message (e.g., the MSG3 414)received from the UE 1004 during the RACH procedure 1040. In otherwords, the base station 1002 may include, in a contention resolutionmessage 1042, an indication of at least a beam index corresponding toone of the beams 1020 a-h through which communication between the basestation 1002 and the UE 1004 is to occur.

Because the contention resolution message 1042 may be received by morethan one UE, the base station 1002 may indicate that the beammodification command included in the contention resolution message 1042is applicable to the UE 1004. In one aspect, the base station 1002 mayindicate that the beam modification command included in the contentionresolution message 1042 is applicable to the UE 1004 by scrambling atleast a portion of the contention resolution message using an RNTIassociated with the UE 1004 (e.g., an RNTI determined during a portionof the RACH procedure 1040).

In one aspect, the beam modification command included in the contentionresolution message 1042 may include an indication of one or morechannels to which the beam modification command is applicable. Forexample, the base station 1002 may determine that communication with theUE 1004 is to occur through the sixth beam 1020 f for one or more uplinkchannels or one or more downlink channels. Therefore, the base station1002 may indicate, in the contention resolution message 1042, that thebeam modification command included in the contention resolution message1042 is applicable to one or more channels.

The UE 1004 may receive the contention resolution message 1042, forexample, during the RACH procedure 1040. As described, the contentionresolution message 1042 may include at least a beam index correspondingto a beam (e.g., a beam modification command).

The UE 1004 may determine whether the beam index is applicable to the UE1004. That is, the UE 1004 may determine whether the base station 1002is instructing the UE 1004 to communicate with the base station 1002through another beam, such as the sixth beam 1020 f. In one aspect, theUE 1004 may determine whether the beam index is applicable to the UE byattempting to decode the contention resolution message 1042 based on anRNTI associated with the UE 1004. If the UE 1004 is able to successfullydecode the contention resolution message 1042 based on the RNTIassociated with the UE 1004, the UE 1004 may determine that the beammodification command indicated by the contention resolution message 1042is applicable to the UE 1004.

The UE 1004 may provide ACK/NACK information to the base station 1002based on the contention resolution message 1042, for example, in orderto indicate that the UE 1004 acknowledges the beam modification command.In an aspect, the UE 1004 may transmit, to the base station 1002, anacknowledgment message 1044 based on a determination that the beammodification command included in the contention resolution message 1042is applicable to the UE 1004. In an aspect, the UE 1004 may transmit theacknowledgment message 1044 through the current beam (e.g., the fifthbeam 1020 e).

In one aspect, the UE 1004 may refrain from transmitting anon-acknowledgment message to the base station 1002 based on adetermination that the beam modification command included in thecontention resolution message 1042 is inapplicable to the UE 1004. Forexample, if the UE 1004 is unable to decode the contention resolutionmessage 1042 based on an RNTI associated with the UE 1004, then the UE1004 may take no action.

The base station 1002 may determine whether an acknowledgment message isreceived from the UE 1004 in response to the contention resolutionmessage 1042. If the base station 1002 determines that an acknowledgmentmessage is unreceived (e.g., absent for a predetermined period of time),the base station 1002 may take no action. For example, the base station1002 may continue communication with the UE 1004 through a currentserving beam, such as the fifth beam 1020 e.

When the base station 1002 receives the acknowledgment message 1044 fromthe UE 1004, the base station 1002 may determine that an acknowledgmentmessage is received from the UE 1004 and the UE 1004 has been informedof the beam modification command. Accordingly, the base station 1002 maycommunicate 1046 through the beam (e.g., the sixth beam 1020 f)corresponding to the beam index indicated by the beam modificationcommand included in the contention resolution message 1042.

Correspondingly, when the UE 1004 determines that the beam modificationcommand is applicable to the UE 1004, the UE 1004 may communicate 1046with the base station through the beam (e.g., the sixth beam 1020 f)corresponding to the beam index indicated by the beam modificationcommand included in the contention resolution message 1042. Because thebeam modification command may include an indication of one or morechannels to which the beam modification command is applicable, the UE1004 may communicate 1046 with the base station 1002 on the one or morechannels indicated by the beam modification command through the beam(e.g., the sixth beam 1020 f) corresponding to the beam index indicatedby the beam modification command (e.g., other communication on otherchannels may occur through another beam, such as the current servingfifth beam 1020 e).

FIG. 11 illustrates an aspect of a wireless communications system 1100,according to various aspects. The base station 1102 may be an aspect ofthe base station 1002, the base station 902, the base station 802, thebase station 702, the base station 602, the base station 502, the basestation 310, the base station 102, the mmW base station 180, and/oranother base station. The UE 1004 may be an aspect of the UE 1004, theUE 904, UE 804, the UE 704, the UE 604, the UE 504, the UE 350, the UE104, the UE 182, and/or another UE.

In the illustrated aspect, the base station 1102 may include up to 8antenna ports for BRS transmission. In various aspects, the base station1102 may send, to the UE 1104, one or more BRSs 1112 a-h (e.g., asdescribed with respect to FIGS. 5A-5G, FIG. 6, FIG. 7, and/or FIG. 8).Each BRS 1112 a-h may be communicated through a respective beam 1120a-h. For example, the base station 1102 may send a first BRS 1112 athrough the first beam 1120 a with which the first BRS 1112 a isassociated. The UE 1104 may track one or more beams 1120 a-h throughperiodically measuring a BRS 1112 a-h associated with a respective oneof the beams 1120 a-h. In an aspect, the transmission period of the BRSs1112 a-h may be configured by an indicator on a PBCH, such as an ePBCH.The transmission period may be associated with the time to sweep thebeams 1120 a-h through which the BRS 1112 a-h is transmitted.

In aspects, the UE 1104 may receive, through the set of transmit beams1120 a-h, a set of BRSs 1112 a-h. Each BRS 1112 a-h may be associatedwith a beam index that corresponds to the beam 1120 a-h through whichthe BRS 1112 a-h is sent. The UE 1104 may measure a signal quality ofeach BRS 1112 a-h, and each measured signal quality may correspond to abeam 1120 a-h of the set of beams. For example, the UE 1104 may measurethe signal qualities of the third BRS 1112 c, the fourth BRS 1112 d, thefifth BRS 1112 e, and the sixth BRS 1112 f, which respectivelycorrespond to the third beam 1120 c, the fourth beam 1120 d, the fifthbeam 1120 e, and the sixth beam 1120 f. In aspects, the UE 1104 may notreceive each of the BRSs 1112 a-h.

In one aspect, the UE 1104 may measure the signal quality by determininga received power. In one aspect, the signal quality may correspond to aBRSRP. For example, the UE 1104 may measure the BRSRP in dB and/or dBm.In other aspects, the UE 1104 may measure the signal quality as anothervalue, such as a RQ, an SIR, a SINR, a RSRP, a RSRQ, a RSSI, or anothermetric.

In one aspect, the UE 1104 may receive the set of BRSs 1112 a-h througha set of receive beams 1140 a-h at the UE 1104. For example, a sixthtransmit beam 1120 f may intersect a fifth receive beam 1140 e.Therefore, a signal sent by the base station 1102 may be transmittedthrough a sixth transmit beam 1120 f and received through a fifthreceive beam 1140 e.

The UE 1104 may not actively maintain all the beams 1140 a-hsimultaneously. In various aspects, the UE 1104 may be configured togenerate one or more of the beams 1140 a-h, for example, based ondetermination that the UE 1104 may receive a signal through one or moreof the receive beams 1140 a-h. Additionally, the base station 1102 andthe UE 1104 may not have an equal number of beams—e.g., the UE 1104 mayhave fewer than eight beams for communication with the base station1102.

In an aspect, the UE 1104 may receive a beam modification command 1142from the base station 1102. For example, the UE 1104 may receive one ormore BRSs 1112 a-h from the base station 1102. The UE 1104 may determine(e.g., select or generate) a receive beam of the set of receive beams1140 a-h through which the UE 1104 may expect to receive signals fromthe base station 1102. For example, the UE 1104 may determine the fourthreceive beam 1140 d through which the UE 1104 may receive signals fromthe base station 1102. The UE 1104 may receive the beam modificationcommand 1142 from the base station 1102, for example, through the fifthtransmit beam 1120 e and the fourth receive beam 1140 d.

In an aspect, the beam modification command 1142 may indicate a set oftransmit beam indexes corresponding to a set of the transmit beams 1120a-h of the base station 1102. For example, the beam modification command1142 may indicate at least a sixth beam index corresponding to a sixthtransmit beam 1120 f of the base station 1102. The transmit beam indexmay indicate at least a transmit direction for transmitting a beam bythe base station 1102.

In one aspect, the beam modification command 1142 may be received in aMAC CE. In another aspect, the beam modification command 1142 may bereceived in a DCI message. In another aspect, the beam modificationcommand 1142 may be received via RRC signaling. In one aspect, the beammodification command 1142 may be carried on PDCCH.

The UE 1104 may determine the set of transmit beam indexes indicated bythe beam modification command 1142. For example, the UE 1104 maydetermine that the beam modification command 1142 indicates at least asixth beam index corresponding to a sixth transmit beam 1120 f of thebase station 1102.

Based on the determined set of transmit beams, the UE 1104 may determinea set of receive beam indexes corresponding to the receive beams 1140a-h of the UE 1104. Each receive beam index may indicate at least areceive direction for receiving a receive beam of the receive beams 1140a-h by the UE 1104. For example, the UE 1104 may determine at least afifth receive beam index corresponding to a fifth receive beam 1140 e ofthe UE 1104.

The UE 1104 may determine the set of receive beam indexes based on thedetermined set of transmit beams indicated by beam modification command1142 in any suitable approach. For example, the UE 1104 may maintain amapping that maps transmit beam indexes corresponding to transmit beams1120 a-h to receive beam indexes corresponding to receive beams 1120a-h.

In one aspect, the UE 1104 may be configured to populate the mappingbased on reception of the set of BRSs 1112 a-h. For example, the UE 1104may receive a sixth BRS 1112 f through a sixth transmit beam 1120 f ofthe base station 1102. The UE 1104 may determine that the sixth BRS 1112f is received through a fifth receive beam 1140 e. Accordingly, the UE1104 may map maintain a mapping that indicates the sixth transmit beamindex corresponding to the sixth transmit beam 1120 f is mapped to thefifth receive beam index corresponding to the fifth receive beam 1140 e.

Thus, when the UE 1104 receives the beam modification command 1142, theUE 1104 may determine at least one of the receive beams 1140 a-h of theUE 1104 through which the UE 1104 may receive signals from the basestation 1102 without the base station 1102 explicitly signaling areceive beam to the UE 1104 (e.g., the base station 1102 may elicit theappropriate receive beams 1140 a-h of the UE 1104 by indicating beamindexes of transmit beams 1120 a-h to the UE 1104). For example, the UE1104 may determine a set of receive beam indexes that correspond to thetransmit beam indexes indicated by the beam modification command 1142.

In an aspect, the UE 1104 may receive communication from the basestation 1102 based on a receive beam corresponding to a receive beamindex, which may be determined based on the beam modification command1142. For example, the UE 1104 may determine that communication from thebase station 1102 may be received through the fifth receive beam 1140 ebased on a transmit beam index corresponding to the sixth transmit beam1120 f indicated by the beam modification command 1142. In one aspect,the UE 1104 may generate the fifth receive beam 1140 e, for example, ifthe fifth receive beam 1140 e is inactive.

The UE 1104 may receive, from the base station 1102, a BRRS 1144 throughthe at least one receive beam determined based on the beam modificationcommand 1142. For example, the UE 1104 may determine a fifth receivebeam index corresponding to the fifth receive beam 1140 e, and the UE1104 may receive the BRRS 1144 through the fifth receive beam 1140 e.

In an aspect, the BRRS 1144 may be used for beam refinement forcommunication—e.g., the BRRS may be used by the UE 1104 and the basestation 1102 in order to determine a “fine” beam pair (e.g., the beampair of transmit beam 1120 f and receive beam 1140 e) for communicationbetween the UE 1104 and the base station 1102. The BRRS 1144 may span 1,2, 5 or 10 OFDM symbols and may be associated with a BRRS resourceallocation, BRRS process indication, and/or a beam refinement processconfiguration. For example, as described in FIGS. 5A-G, the UE 1104 mayreport BRI for beam refinement based on reception of a BRRS.

In one aspect, the UE 1104 may receive the BRRS 1144 in one or moresymbols corresponding to one or more respective symbol indexes. Forexample, one or more symbol indexes may be predetermined (e.g., definedby one or more standards promulgated by 3GPP), and the UE 1104 may havethose predetermined symbol indexes stored therein. Accordingly, the UE1104 may receive the BRRS 1144 at those symbol indexes.

In another aspect, the beam modification command 1142 may indicate oneor more symbol indexes in which the BRRS 1144 is to be received. Forexample, the beam modification command 1142 may indicate that the BRRS1144 is carried in a fourth symbol of a subframe through a sixthtransmit beam 1120 f. Accordingly, the UE 1104 may determine that the UE1104 is to receive at least a portion of the BRRS 1144 using a fifthreceive beam 1140 e during a fourth symbol of a subframe (e.g., the UE1104 may actively receive or listen through the fifth receive beam 1140e during a fourth symbol of a subframe).

In one aspect, the UE 1104 may receive different portions of the BRRS1144 through different receive beams. For example, the UE may receive afirst portion of the BRRS 1144 (e.g., the first symbol or first 5symbols) of the BRRS 1144 through the fifth receive beam 1140 edetermined based on the beam modification command 1142, and may receivea second portion of the BRRS 1144 (e.g., the second symbol or next 5symbols) of the BRRS 1144 through the sixth receive beam 1140 f, whichmay also be determined based on the beam modification command 1142(e.g., included in the set of receive beam indexes determined based onthe beam modification command).

In an aspect, the UE 1104 may determine symbol indexes corresponding tosymbols of the BRRS 1144 and receive beam indexes corresponding to thosesymbol indexes. For example, the beam modification command 1142 mayindicate a first set of transmit beam indexes corresponding to the fifthtransmit beam 1120 e and the sixth transmit beam 1120 f. The UE 1104 maydetermine (e.g., based on the beam modification command 1142 and/orbased on predetermined symbol indexes) that a first portion of the BRRS1144 is to be received through the fifth transmit beam 1120 e and asecond portion of the BRRS 1144 is to be received through the sixthtransmit 1120 f. The UE 1104 may determine the fourth receive beam 1140d and the fifth receive beam 1140 e respectively corresponding to thetransmit beam indexes for the fifth transmit beam 1120 e and the sixthtransmit beam 1120 f. Accordingly, the UE 1104 may receive a firstportion of the BRRS 1144 (e.g., the first symbol or first 5 symbols)through the fourth receive beam 1140 d and receive a second portion ofthe BRRS 1144 (e.g., the next symbol or next 5 symbols) through thefifth receive beam 1140 e.

In an aspect, the UE 1104 may receive the BRRS 1144 through the set oftransmit beams of the base station 1102 corresponding to the set oftransmit beam indexes indicated by the beam modification command 1142(e.g., through the sixth transmit beam 1120 f).

In another aspect, the UE 1104 may receive the BRRS 1144 through adifferent set of transmit beams of the base station than those transmitbeams corresponding to the transmit beam indexes indicated by the beammodification command 1142. For example, the UE 1104 may determine to usethe fifth receive beam 1140 e based on a transmit beam indexcorresponding to the sixth transmit beam 1120 f, but the BRRS 1144 maybe transmitted through the fifth transmit beam 1120 e (e.g., due toreflection or obstruction).

FIG. 12 is a flowchart of a method 1200 of wireless communication. Themethod 1200 may be performed by a UE, such as the UE 1104, the UE 1004,the UE 904, the UE 804, the UE 704, the UE 604, the UE 504, the UE 404,the UE 350, the UE 104, the UE 182, or another UE. In one aspect, themethod 1200 may be performed by an apparatus, such as the apparatus1902/1902′. One of ordinary skill would understand that one or moreoperations may be omitted, transposed, and or performedcontemporaneously.

At operation 1202, the UE may communicate with a base station through aserving beam corresponding to a serving beam index. For example, the UEmay send at least one signal through the serving beam corresponding tothe serving beam index. In the context of FIG. 7, the UE 704 maycommunicate with the base station 702 through the first serving beam 720e, which may correspond to a beam index.

At operation 1204, the UE may receive, from the base station, a beammodification command. In aspects, the beam modification command mayindicate at least a beam index for communicating through at least onebeam on at least one channel. In aspects, each beam index of the atleast one beam index indicates at least a direction for communicatingthrough a corresponding beam of the at least one beam. In the context ofFIG. 7, the UE 704 may receive, from the base station 702, the beammodification command 710.

In one aspect, the beam modification command is received in a MAC CE. Inanother aspect, the beam modification command is received in a DCImessage. In another aspect, the beam modification command is receivedvia RRC signaling.

According to an aspect, the beam modification command may indicate, foreach beam index of the at least one beam index, a corresponding channel.Thus, communication carried on the corresponding channel may occurthrough the at least one beam corresponding to the at least one beamindex indicated by the beam modification command. For example, the beammodification command may indicate that the at least one beam indexcorresponds to one or more uplink channel(s) and/or one or more downlinkchannel(s). In one aspect, the UE may determine the correspondingchannel based on a DCI format of the DCI message.

In one aspect, the at least one beam index may be a plurality of beamindexes, and the at least one channel may be a plurality of channels. Insuch an aspect, each beam index of the plurality of beam indexes may beindicated as corresponding to at least one channel of the plurality ofchannels. In the context of FIG. 7, the UE 704 may receive, from thebase station 702, the beam modification command 710 that indicates achannel corresponding to each beam index.

At operation 1206, the UE may switch, after receiving the beammodification command, from the serving beam to the at least one beamcorresponding to the at least one beam index indicated by the beammodification command. For example, the UE may select the at least onebeam corresponding to the at least one beam index, and the UE may changefrom the serving beam to the at least one beam for communication withthe base station. In the context of FIG. 7, the UE 704 may switch, afterreceiving the beam modification command 710, from the first serving beam720 e to the selected fourth beam 720 d, which may correspond to the atleast one beam index indicated by the beam modification command 710.

In one aspect, the UE may switch from the serving beam to the at leastone beam corresponding to the beam index indicated by the beammodification command at a predetermined time. In one aspect, UE maydetermine the predetermined time based on the beam modification command.For example, the beam modification command may indicate at least one ofa symbol or a subframe at which the UE is to switch from the servingbeam to the at least one beam corresponding to the beam index indicatedby the beam modification command. In the context of FIG. 7, the UE 704may switch from the first serving beam 720 e to the selected fourth beam720 d at a predetermined time (e.g., a symbol or subframe indicated bythe beam modification command 710).

At operation 1208, the UE may determine at least one channel on whichcommunication with the base station is to occur through the at least onebeam corresponding to the beam index indicated by the beam modificationcommand. For example, the UE may identify the at least one channel(e.g., based on the beam modification command), and the UE may associatethe at least one channel with the at least one beam index. In oneaspect, the UE may determine that at least one channel based on a DCIformat when the beam modification command is included in a DCI message.In the context of FIG. 7, the UE 704 may determine at least one channelon which communication is to occur through the at least one beamcorresponding to the beam index indicated by the beam modificationcommand 710.

At operation 1210, the UE may communicate, with the base station,through the at least one beam corresponding to the beam index indicatedby the beam modification command. The UE may communicate with the basestation through the at least one beam on at least one channel (e.g., oneor more uplink channels or one or more downlink channels). In thecontext of FIG. 7, the UE 704 may communicate, with the base station702, through the selected fourth beam 720 d corresponding to the atleast one beam index indicated by the beam modification command 710. TheUE 704 may communicate with the base station 702 through the selectedfourth beam 720 d on one or more channels (e.g., one or more uplinkchannels or one or more downlink channels).

FIG. 13 is a flowchart of a method 1300 of wireless communication. Themethod 1300 may be performed by a UE, such as the UE 1104, the UE 1004,the UE 904, the UE 804, the UE 704, the UE 604, the UE 504, the UE 404,the UE 350, the UE 104, the UE 182, or another UE. In one aspect, themethod 1200 may be performed by an apparatus, such as the apparatus2102/2102′. One of ordinary skill would understand that one or moreoperations may be omitted, transposed, and or performedcontemporaneously.

At operation 1302, the UE may receive, from a base station, through aset of beams a set of BRSs. In the context of FIG. 6, the UE 604 mayreceive, from the base station 602, a set of BRSs 612 a-h through a setof beams 620 a-h. For example, the UE 604 may receive a third BRS 612 cthrough a third beam 620 c, a fourth BRS 612 d through a fourth beam 620d, a fifth BRS 612 e through a fifth beam 620 e, and a sixth BRS 612 fthrough a sixth beam 620 f.

At operation 1304, the UE may measure a respective signal quality ofeach BRS of the set of BRSs. For example, the UE may identify a BRS ofthe set of BRSs, and the UE may measure a signal quality for theidentified BRS. As each BRS may correspond to a beam, a signal qualitymeasured for a BRS may also correspond to that beam through which theBRS is received. According to various aspects, the measurement of thesignal quality of each BRS of the set of BRSs may include measurement ofat least one of a BRSRP, a BRSRQ, an SIR, an SINR, and/or an SNR. In thecontext of FIG. 6, the UE 604 may measure a respective signal qualityfor each received BRS of the set of BRSs 612 a-h, and a respectivesignal quality may correspond to a respective beam of the set of beams620 a-h.

At operation 1306, the UE may receive, from the base station, anindication of one or more beam indexes that are to be excluded from aset of candidate beam indexes. In the context of FIG. 6, the UE 604 mayreceive, from the base station 602, an indication of one or more beamindexes that are to be excluded from a set of candidate beam indexes630.

At operation 1308, the UE may maintain a set of candidate beam indexescorresponding to a set of best measured signal qualities of the set ofBRSs. For example, the UE may identify a beam index and a correspondingmeasured signal quality, and the UE may store (e.g., in a table or otherdata structure) the identified beam index in association with thecorresponding measured signal quality. With respect to operation 1306,the UE may exclude one or more beam indexes indicated by the basestation from the maintained set of candidate beam indexes. In oneaspect, the UE may maintain a set of N candidate beam indexes, and N maybe predetermined (e.g., stored in the UE, defined by a standardpromulgated by 3GPP, etc.). In the context of FIG. 6, the UE 604 maymaintain the set of candidate beam indexes 630 corresponding to a set ofbest measured signal qualities for the set of BRSs 612 a-h.

In one aspect, the set of measured signal qualities may be a set of thehighest measured signal qualities. In the context of FIG. 6, the set ofcandidate beam indexes may reflect the highest measured BRSRPs for thereceived set of BRSs 612 c-f corresponding to the set of beams 620 c-f.

In one aspect, the set of best measured signal qualities of the set ofBRSs may be based on a most recent set of signal qualities of the set ofBRSs. In another aspect, the set of best measured signal qualities ofthe set of BRSs may be based on a filtered set of signal qualities ofthe set of BRSs. In another aspect, the set of best measured signalqualities of the set of BRSs may be based on a time-averaged set ofsignal qualities of the set of BRSs. In one aspect, the set of bestmeasured signal qualities may be maintained based on at least onehysteresis criteria for including a beam index in or excluding a beamindex from the set of candidate beam indexes.

At operation 1310, the UE may transmit, to the base station, BSIindicating at least one measured signal quality and at least one beamindex corresponding to the at least one measured signal quality. In thecontext of FIG. 6, the UE 604 may transmit, to the base station 602, aBSI report 642 indicating at least one beam index. In an aspect, the BSIreport 642 may be a BSI report that includes a beam index and acorresponding measured signal quality (e.g., the BRSRP measured for aBRS 612 a-h received through a beam 620 a-h). In an aspect, the UE 604may transmit the BSI report 642 in response to a request 640 receivedfrom the base station 602.

FIG. 14 is a flowchart of a method 1400 of wireless communication. Themethod 1400 may be performed by a UE, such as the UE 1104, the UE 1004,the UE 904, the UE 804, the UE 704, the UE 604, the UE 504, the UE 404,the UE 350, the UE 104, the UE 182, or another UE. In one aspect, themethod 1200 may be performed by an apparatus, such as the apparatus2302/2302′. One of ordinary skill would understand that one or moreoperations may be omitted, transposed, and or performedcontemporaneously.

At operation 1402, the UE may receive, from a base station, a set ofsignals through a set of beams. In the context of FIG. 8, the UE 804 mayreceive, from the base station 802, a set of BRSs 812 a-h through a setof beams 820 a-h. For example, the UE 804 may receive a third BRS 812 cthrough a third beam 820 c, a fourth BRS 812 d through a fourth beam 820d, a fifth BRS 812 e through a fifth beam 820 e, and a sixth BRS 812 fthrough a sixth beam 820 f.

At operation 1404, the UE may determine a received power for each signalof the set of signals received through each beam of the set of beams.For example, the UE may identify the signal, and the UE may measure areceived power corresponding to the identified signal. Each determinedreceived power may be associated with a respective beam of the set ofbeams (e.g., each BRS may correspond to a beam and, therefore, areceived power determined for a BRS may also correspond to that beamthrough which the BRS is received). According to various aspects, thedetermination of the received power of each BRS of the set of BRSs mayinclude measurement of at least one of a BRSRP, a BRSRQ, an SIR, anSINR, and/or an SNR. In the context of FIG. 6, the UE 604 may determinea received power for each received BRS of the set of BRSs 612 a-h, and arespective received power may correspond to a respective beam of the setof beams 620 a-h.

At operation 1406, the UE may receive, from the base station, a messagerequesting BSI. In one aspect, a DCI message (e.g., a downlink DCImessage or an uplink DCI message) may include the message requestingBSI. In another aspect, an RAR message may include the messagerequesting BSI. In the context of FIG. 8, the UE 804 may receive, fromthe base station 802, the message 840 requesting BSI.

At operation 1408, the UE may determine a number N of BSI reports tosend to the base station, and each BSI report may indicate a beam indexcorresponding to a beam and a received power associated with the beam.For example, the UE may identify the message from the base stationrequesting BSI, and the UE may identify the number N of BSI reports tosend based on the identified message. In the context of FIG. 8, the UE804 may determine a number N of BSI reports 842 to send to the basestation 802. Each BSI report 842 may include at least one of the beamindexes 832 c-f and a BRSRP 834 c-f corresponding to the at least one ofthe beam indexes 832 c-f.

In an aspect, the UE may determine the number N based on the messagerequesting BSI (e.g., based on the type of message). For example, the UEmay determine that the number N is one when the message requesting BSIis included in a DCI message (e.g., a downlink DCI message). In anotheraspect, the UE may determine that the number N is greater than one(e.g., two or four) when the message requesting BSI is included in anRAR message (or an uplink DCI message); the number N greater than onemay be indicated by the message (e.g., the message requesting BSI mayindicate that the UE is to send two or four BSI reports). In the contextof FIG. 8, the UE 804 may determine the number N of BSI reports 842 tosend to the base station 802 based on the message 840 (e.g., the type orformat of the message 840).

In one aspect, the UE may determine a channel that is to carry the BSIreports based on the message. For example, the UE may determine that thenumber N of BSI reports are to be carried on a PUCCH when the number Nis one and/or when the message requesting BSI is included in a DCImessage (e.g., a downlink DCI message). In another aspect, the UE maydetermine that the number N of BSI reports are to be carried on a PUSCHwhen the number N is greater than one and/or when the message requestingBSI is included in an RAR message (or an uplink DCI message).

At operation 1410, the UE may send, to the base station, N BSI reportsbased on the message requesting BSI. In an aspect, the N BSI reportsinclude N received powers corresponding to the highest determinedreceived powers and the beam indexes corresponding to those highestdetermined received powers. In the context of FIG. 8, the UE 804 maysend, to the base station 802, N BSI reports 842 based on the message840. For example, at least one BSI report 842 may include a fifth beamindex 832 e and a corresponding BRSRP 834 e, which may be the highestBRSRP of the BRSRPs measured for the BRSs 812 a-h received through thebeams 820 a-h.

FIG. 15 is a flowchart of a method 1500 of wireless communication. Themethod 1500 may be performed by a UE, such as the UE 1104, the UE 1004,the UE 904, the UE 804, the UE 704, the UE 604, the UE 504, the UE 404,the UE 350, the UE 104, the UE 182, or another UE. In one aspect, themethod 1200 may be performed by an apparatus, such as the apparatus2502/2502′. One of ordinary skill would understand that one or moreoperations may be omitted, transposed, and or performedcontemporaneously.

At operation 1502, the UE may select a first beam for communication witha base station. For example, the UE may select a beam indexcorresponding to a beam through which the UE estimates or expects thebase station to be able to communicate with the UE. In the context ofFIG. 9, the UE 904 may select the fifth beam 920 e as the first beam forcommunication with the base station 902.

At operation 1504, the UE may attempt at least one RACH procedure withthe base station through the selected beam. For example, the UE may sendat least one RACH message (e.g., the MSG1 410) to the base station, andthe UE may determine that a response to the at least one RACH message isabsent (e.g., not received within a predetermined period of time). Inthe context of FIG. 9, the UE 904 may attempt a first RACH procedure 940with the base station 902 through the selected fifth beam 920 e.

At operation 1506, the UE may determine that the at least one RACHprocedure failed. For example, the UE may start a timer in associationwith one or more messages, and the UE may fail to receive or decode oneor more messages associated with the at least one RACH procedure (e.g.,a MSG2 or RAR, a MSG4 or contention resolution message, etc.) beforeexpiration of the timer. In the context of FIG. 9, the UE 904 maydetermine that the first RACH procedure 940 failed with the base station902.

At operation 1508, the UE may select a new beam for communication withthe base station after the determination that the at least one RACHprocedure failed. For example, the UE may access a stored set ofcandidate beam indexes, and the UE may select a next beam correspondingto a next beam index in a set of candidate beam indexes (e.g., a beamcorresponding to a next highest BRSRP). In the context of FIG. 9, the UE904 may select the sixth beam 920 f for communication with the basestation 902 after the determination that the first RACH procedure 940failed.

At operation 1510, the UE may increase a transmission power after thedetermination that the at least one RACH procedure failed. For example,the UE may identify a current transmission power, and the UE mayincrease the identified current transmission power by a predeterminedamount. In the context of FIG. 9, the UE 904 may increase a transmissionpower for the successful RACH procedure 942.

In an aspect, the UE may perform one or both of operations 1508 and1510. In other words, the UE may increase a transmission power andattempt another RACH procedure through the selected first beam (e.g.,instead of selecting a new beam for attempting another RACH procedure).Alternatively, the UE may use a same transmission power when attemptinganother RACH procedure through a newly selected beam. Alternatively, theUE may both increase transmission power and use a newly selected beamwhen attempting another RACH procedure after a determination that thefirst RACH procedure failed.

At operation 1512, the UE may store information associated with theselected first beam based on the determination that the at least oneRACH procedure failed. For example, the UE may generate or access a datastructure, and the UE may store a beam index corresponding to the firstbeam through which the UE attempted the failed RACH procedure (e.g., inthe generated or accessed data structure). In an aspect, the UE mayexclude the beam index corresponding to the first beam from a set ofcandidate beam indexes maintained by the UE based on the determinationthat the at least one RACH procedure failed. In another example, the UEmay store an indication of a subframe in which a RACH message associatedwith the failed RACH procedure is carried (e.g., a MSG1 or random accesspreamble, a MSG3 or connection request message, etc.).

At operation 1514, the UE may perform a successful RACH procedure withthe base station. For example, the UE may send a connection requestmessage (e.g., the MSG3 414) and the UE may receive a contentionresolution message (e.g., the MSG4 416) in response to the connectionrequest message. The UE may be synchronized with a network that includesthe base station based on the successful RACH procedure. In the contextof FIG. 9, the UE 904 may perform the successful RACH procedure 942 withthe base station 902, for example, through the sixth beam 920 f.

At operation 1516, the UE may send, after the successful RACH procedurewith the base station, information indicating that the at least one RACHprocedure failed. In an aspect, this information may be the informationstored as described at operation 1512. For example, this information mayinclude a beam index corresponding to the first beam and/or anindication of a subframe in which a message associated with the failedRACH procedure was carried. In one aspect, this information may beincluded in a BSI report. In the context of FIG. 9, the UE 904 may send,after the successful RACH procedure 942, information 944 indicating thatthe first RACH procedure 940 failed.

FIG. 16 is a flowchart of a method 1600 of wireless communication. Themethod 1500 may be performed by a UE, such as the UE 1104, the UE 1004,the UE 904, the UE 804, the UE 704, the UE 604, the UE 504, the UE 404,the UE 350, the UE 104, the UE 182, or another UE. In one aspect, themethod 1200 may be performed by an apparatus, such as the apparatus2702/2702′. One of ordinary skill would understand that one or moreoperations may be omitted, transposed, and or performedcontemporaneously.

At operation 1602, the UE may receive, from a base station, a contentionresolution message indicating at least one beam index corresponding to abeam. In the context of FIG. 10, the UE 1004 may receive, from the basestation 1002, the contention resolution message 1042, for example, aspart of the RACH procedure 1040. For example, the UE 1004 may receive,from the base station 1002, the contention resolution message 1042through the fifth beam 1020 e, and the contention resolution message1042 may indicate a beam index corresponding to the sixth beam 1020 f.

In an aspect, the contention resolution message may be received as partof a RACH procedure. The contention resolution message may also be knownas a MSG4. In the context of FIG. 4A, the contention resolution messagemay be an aspect of the MSG4 416. Accordingly, the UE 404 may receive,from the base station 402, the MSG4 416, for example, according to aRACH procedure.

In an aspect, the contention resolution message may indicate one or morechannels to which the at least one beam index corresponding to the beamis applicable. For example, the contention resolution message mayindicate that the at least one beam index corresponding to the beam isapplicable to one or more uplink channels and/or one or more downlinkchannels. In the context of FIG. 10, the contention resolution message1042 may indicate one or more channels to which the at least one beamindex corresponding to the beam is applicable. Accordingly, the UE 1004may determine, based on the contention resolution message 1042, one ormore channels to which the at least one beam index corresponding to thebeam is applicable.

At operation 1604, the UE may determine whether the beam index isapplicable to the UE. In other words, the UE may determine whethercommunication with the base station is to occur through the beamcorresponding to the beam index indicated by the contention resolutionmessage. In the context of FIG. 10, the UE 1004 may determine whetherthe beam index indicated by the contention resolution message 1042 isapplicable to the UE 1004.

In an aspect, operation 1604 may include operation 1620. At operation1620, the UE may attempt to decode the contention resolution messagebased on an RNTI associated with the UE. When the UE successfullydecodes the contention resolution message based on an RNTI associatedwith the UE, the UE may determine that the beam index indicated by thecontention resolution is applicable to the UE. When the UE is unable tosuccessfully decode the contention resolution message based on an RNTIassociated with the UE, the UE may determine that the beam index isinapplicable to the UE. In the context of FIG. 10, the UE 1004 mayattempt to decode the contention resolution message 1042 based on anRNTI associated with the UE 1004 (e.g., an RNTI determined during theRACH procedure 1040).

When the UE determines that the beam index indicated by the contentionresolution message is applicable to the UE, the method 1600 may proceedto operation 1606. At operation 1606, the UE may transmit, to the basestation, an acknowledgment message e.g., the UE may transmit ACKfeedback indicating that the UE acknowledges the contention resolutionmessage received from the base station. In one aspect, the UE maytransmit the acknowledgment message through the beam used for the RACHprocedure. In another aspect, the UE may transmit the acknowledgmentmessage through the beam corresponding to the beam index indicated bythe contention resolution message. In the context of FIG. 10, the UE1004 may transmit, to the base station 1002, the acknowledgment message1044 based on the determination that the beam index indicated by thecontention resolution message 1042 is applicable to the UE.

At operation 1608, the UE may communicate with the base station throughthe beam corresponding to the beam index indicated by the contentionresolution message. In an aspect, the UE may switch from a currentserving beam to a new beam, and the new beam may correspond to the beamindex indicated by the contention resolution message. In an aspect, theUE may communicate with the base station through the beam correspondingto the beam index indicated by the contention resolution message on oneor more channels (e.g., one or more uplink channels or one or moredownlink channels), which may also be indicated by the contentionresolution message. In the context of FIG. 10, the UE 1004 maycommunicate 1046 with the base station 1002 through the sixth beam 1020f, and the sixth beam 1020 f may correspond to the beam index indicatedby the contention resolution message 1042.

When the UE determines that the beam index indicated by the contentionresolution message is inapplicable to the UE or if the UE is unable tosuccessfully decode the contention resolution message, the method 1600may proceed to operation 1610. At operation 1610, the UE may refrainfrom transmitting a non-acknowledgment message to the base station whenthe beam index is determined to be inapplicable to the UE or if the UEis unable to successfully decode the contention resolution message. Forexample, the UE may refrain from transmitting NACK feedback to the basestation. In the context of FIG. 10, the UE 1004 may refrain fromtransmitting a non-acknowledgment message to the base station when theUE 1004 determines that the beam index indicated by the contentionresolution message 1042 is inapplicable to the UE 1004 or when the UE1004 is unable to successfully decode the contention resolution message1042.

At operation 1612, the UE may continue to communicate with the basestation through a current serving beam. For example, the UE may continueto communicate with the base station through the beam used for the RACHprocedure with which the contention resolution message is associated(e.g., the UE may attempt a second RACH procedure through the same beamused for the first RACH procedure). In the context of FIG. 10, the UE1004 may continue to communicate with the base station 1002 through thefifth beam 1020 e used for the first RACH procedure 1040 (e.g., the UE1004 may attempt another RACH procedure similar to the first RACHprocedure 1040 through the fifth beam 1020 e used for the first RACHprocedure 1040).

FIG. 17 is a flowchart of a method 1700 of wireless communication. Themethod 1700 may be performed by a base station, such as the base station1102, the base station 1002, the base station 902, the base station 802,the base station 702, the base station 602, the base station 502, thebase station 402, the base station 310, the base station 102, the basestation 180, or another base station. In one aspect, the method 1200 maybe performed by an apparatus, such as the apparatus 2902/2902′. One ofordinary skill would understand that one or more operations may beomitted, transposed, and or performed contemporaneously.

At operation 1702, the base station may scramble at least a portion of acontention resolution message using an RNTI associated with a UE. Forexample, the base station may identify an RNTI associated with the UE,and encode at least a portion of the contention resolution message usingthe identified RNTI. In the context of FIG. 10, the base station 1002may scramble at least a portion of the contention resolution message1042 using an RNTI associated with the UE 1004.

At operation 1704, the base station may transmit, to the UE, thecontention resolution message indicating at least one beam indexcorresponding to a beam and further indicating that the beam index isapplicable to the UE. The base station may indicate that the beam indexis applicable to the UE by scrambling at least a portion of thecontention resolution message using an RNTI associated with the UE, asdescribed at operation 1702. In one aspect, the base station may selecta beam for communication with the UE, and the selected beam may bedifferent from the beam through which the contention resolution messageis transmitted. In the context of FIG. 10, the base station 1002 maytransmit, to the UE 1004, the contention resolution message 1042. Thebase station 1002 may transmit the contention resolution message 1042through the fifth beam 1020 e, and the contention resolution message1042 may indicate a beam index corresponding to the sixth beam 1020 f.

In an aspect, the contention resolution message may be generated by thebase station as part of a RACH procedure. The contention resolutionmessage may also be known as a MSG4. The contention resolution messagemay be generated by the base station in response to a connection requestmessage or MSG3 received from the UE as part of a RACH procedure. In thecontext of FIG. 4A, the contention resolution message may be an aspectof the MSG4 416. Accordingly, the base station 402 may transmit, to theUE 404, the MSG4 416, for example, according to a RACH procedure.

In an aspect, the contention resolution message may indicate one or morechannels to which the at least one beam index corresponding to the beamis applicable. For example, the contention resolution message mayindicate that the at least one beam index corresponding to the beam isapplicable to one or more uplink channels and/or one or more downlinkchannels. In the context of FIG. 10, the contention resolution message1042 may indicate one or more channels to which the at least one beamindex corresponding to the beam is applicable. For example, the basestation 1002 may indicate, by the contention resolution message 1042,one or more channels to which the at least one beam index correspondingto the beam is applicable.

At operation 1706, the base station may determine whether anacknowledgment message is received from the UE in response to thecontention resolution message. In the context of FIG. 10, the basestation 1002 may determine whether the acknowledgment message 1044 isreceived from the UE 1004 in response to the contention resolutionmessage 1042.

When the base station determines that the acknowledgment message isreceived from the UE, the method 1700 may proceed to operation 1708. Atoperation 1708, the base station may communicate with the UE through thebeam corresponding to beam index indicated by the contention resolutionmessage. In an aspect, the base station may communicate with the UEthrough the beam corresponding to the beam index indicated by thecontention resolution message on one or more channels (e.g., one or moreuplink channels or one or more downlink channels), which may also beindicated by the contention resolution message. In the context of FIG.10, the base station 1002 may communicate 1046 with the UE through thesixth beam 1020 f, and the sixth beam 1020 f may correspond to the beamindex indicated by the contention resolution message 1042.

When the base station determines that the acknowledgment message is notreceived from the UE, the method 1700 may proceed to operation 1710. Atoperation 1710, the base station may communicate with the UE through acurrent serving beam, such as the beam used for the RACH procedure withwhich the contention resolution message is associated. In one aspect,the base station may take no action with the UE when the base stationdetermines that the acknowledgment message is not received from the UE.In the context of FIG. 10, the base station 1002 may communicate withthe UE through the fifth beam 1020 e, which may be the beam throughwhich one or more messages associated with the RACH procedure 1040 arecommunicated.

FIG. 18 is a flowchart of a method 1800 of wireless communication. Themethod 1800 may be performed by a UE, such as the UE 1104, the UE 1004,the UE 904, the UE 804, the UE 704, the UE 604, the UE 504, the UE 404,the UE 350, the UE 104, the UE 182, or another UE. In one aspect, themethod 1200 may be performed by an apparatus, such as the apparatus3102/3102′. One of ordinary skill would understand that one or moreoperations may be omitted, transposed, and or performedcontemporaneously.

At operation 1802, the UE may receive a beam modification command thatindicates a set of transmit beam indexes corresponding to a set oftransmit beams of a base station. Each transmit beam index of the set oftransmit beam indexes may indicate at least a direction for transmittinga transmit beam by the base station. In the context of FIG. 11, the UE1104 may receive, from the base station 1102, the beam modificationcommand 1142 that indicates a set of transmit beam indexes correspondingto a set of transmit beams 1120 a-h of the base station 1102.

In an aspect, the beam modification command may be received in a MAC CE.In an aspect, the beam modification command may be received in a DCImessage. In an aspect, the beam modification command may be received viaRRC signaling. In an aspect, the beam modification command may becarried on a PDCCH.

At operation 1804, the UE may determine a set of receive beam indexescorresponding to a set of receive beams of the UE based on the set oftransmit beam indexes. Each receive beam index of the set of receivebeam indexes may indicate at least a receive direction for receiving abeam by the UE. In an aspect, the UE may determine the set of receivebeam indexes by accessing a mapping that maps transmit beam indexes toreceive beam indexes. The UE may be configured to populate this mapping.The UE may identify at least one receive beam index corresponding to atleast one transmit beam index based on the accessed mapping.

In the context of FIG. 11, the UE 1104 may determine a set of receivebeam indexes corresponding to a set of receive beams 1140 a-h of the UE1104 based on the set of transmit beam indexes indicated by the beammodification command 1142. For example, the UE 1104 may determine a setof receive beam indexes corresponding to the fourth receive beam 1140 dand the fifth receive beam 1140 e based on a set of transmit beamindexes corresponding to the fifth transmit beam 1120 e and the sixthtransmit beam 1120 f, respectively.

At operation 1806, the UE may receive, from the base station, a BRRSthrough at least one receive beam corresponding to at least one receivebeam index included in the determined set of receive beam indexes. Inone aspect, the UE may generate a receive beam corresponding to the atleast one receive beam index, for example, when the UE is not activelymaintaining that beam. In the context of FIG. 11, the UE 1104 mayreceive, from the base station 1102, the BRRS 1144 through at least thefifth receive beam 1140 e corresponding to at least one receive beamindex included in the determined set of receive beam indexes.

In one aspect, the UE may receive the BRRS through the set of transmitbeams from the base station corresponding to the set of transmit beamindexes. In another aspect, the UE may receive the BRRS through adifferent set of transmit beams from the base station than the set oftransmit beams corresponding to the transmit beam indexes indicated bythe beam modification command. For example, obstruction and/orreflection may cause the UE to receive the BRRS through the determinedset of receive beams, but through a different set of transmit beams thanthe set of transmit beams corresponding to the set of transmit beamindexes indicated by the beam modification command.

In one aspect, the UE may receive the BRRS in one or more symbolscorresponding to one or more symbol indexes. For example, the UE mayreceive (e.g., listen) through the at least one receive beamcorresponding to the at least one receive beam index during one or moresymbols corresponding to the one or more symbol indexes. In an aspect,the one or more symbol indexes may be predetermined (e.g., defined byone or more standards promulgated by 3GPP). In another aspect, the oneor more symbol indexes may be indicated by the beam modificationcommand. In one aspect, the beam modification command further indicatesa corresponding transmit beam index of the set of transmit beam indexesfor each symbol of the one or more symbol indexes.

In an aspect, operation 1806 may include operation 1820 and operation1822. At operation 1820, the UE may receive a first portion of the BRRSin a first set of symbols through a first receive beam corresponding toa first receive beam index included in the determined set of receivebeam indexes. In the context of FIG. 11, the UE 1104 may receive a firstportion of the BRRS 1144 in a first set of symbols through the fourthreceive beam 1140 d corresponding to a fourth receive beam index, whichmay be determined based on a fifth transmit beam index corresponding toa fifth transmit beam 1120 e indicated by the beam modification command1142.

At operation 1822, the UE may receive a second portion of the BRRS in asecond set of symbols through a second receive beam corresponding to asecond receive beam index included in the determined set of receive beamindexes. In the context of FIG. 11, the UE 1104 may receive a secondportion of the BRRS 1144 in a second set of symbols through the fifthreceive beam 1140 d corresponding to a fifth receive beam index, whichmay be determined based on a sixth transmit beam index corresponding toa sixth transmit beam 1120 f indicated by the beam modification command1142.

FIG. 19 is a conceptual data flow diagram 1900 illustrating the dataflow between different means/components in an exemplary apparatus 1902.The apparatus may be a UE. The data flow illustrated in the diagram 1900is to be regarded as illustrative. Therefore, one or more additionalmeans/components may be present, and one or more illustratedmeans/components may be absent, according to various aspects. Further,various data flow may occur between means/components in addition to theillustrated data flow.

The apparatus 1902 may include a reception component 1904 configured toreceive signals from a base station (e.g., the base station 1950, a mmWbase station, an eNB, etc.). The apparatus 1902 may further include atransmission component 1910 configured to transmit signals to a basestation (e.g., the base station 1950, a mmW base station, an eNB, etc.).

In an aspect, the apparatus 1902 may include a communication component1912. The communication component 1912 may be configured to receive,through the reception component 1904, downlink data and/or controlinformation. The communication component may be configured to determine(e.g., generate, select, etc.) uplink data and/or control informationthat is to be sent to the base station 1950 via the transmissioncomponent 1910. In aspects, the communication component 1912 maycommunicate, with the base station 1950, through a serving beamcorresponding to a serving beam index. In one aspect, the communicationcomponent 1912 may communicate through a first beam corresponding to afirst beam index for downlink communication received from the basestation 1950 and communicate through a second beam corresponding to asecond beam index for uplink communication sent to the base station1950. The first beam and the second beam are not necessarily the samebeam. Therefore, uplink communication and downlink communication mayoccur through different beams.

The apparatus 1902 may include an identification component 1906. Theidentification component 1906 may receive a beam modification commandfrom the base station. The beam modification command may indicate atleast one beam index for communicating through at least one beam on atleast one channel—each beam index may indicate at least a direction forcommunicating through a corresponding beam of the at least one beam. Inan aspect, the beam modification command may indicate a plurality ofbeam indexes. The identification component 1906 may determine, based onthe beam modification command, at least one beam index for communicatingthrough at least one beam on at least one channel.

In one aspect, the identification component 1906 may receive the beammodification command in a MAC CE. In another aspect, the identificationcomponent 1906 may receive the beam modification command in a DCImessage. In another aspect, the identification component 1906 mayreceive the beam modification command via RRC signaling.

In one aspect, the identification component 1906 may further determineat least one channel corresponding to at least one determined beamindex. For example, the identification component 1906 may determine thatthe beam modification command is be applicable to one or more uplinkchannels for uplink communication and/or is applicable to one or moredownlink channels for downlink communication. In one aspect, theidentification component 1906 may determine a plurality of channelscorresponding to the at least one beam index.

The identification component 1906 may determine the at least one channelbased on the beam modification command. For example, the identificationcomponent 1906 may determine the at least one channel based on a DCIformat of a DCI message that indicates the at least one beam index. Inan aspect, the identification component may determine, for each beamindex, a corresponding channel to which each beam index is applicable.

The identification component 1906 may provide, to a selection component1908, beam index information that includes the at least one determinedbeam index. In an aspect, the identification component 1906 may provide,to the selection component 1908, beam index information indicating oneor more channels to which each beam index is applicable. For example,the identification component 1906 may provide, to the selectioncomponent 1908, a beam index and an indication that the beam index isapplicable to uplink channels for uplink communication or downlinkchannels for downlink communication.

In an aspect, the selection component 1908 may be configured todetermine whether a first serving beam is to be switched based on thebeam index information. The selection component 1908 may instruct thecommunication component 1912 to switch from the first serving beam to asecond serving beam.

In an aspect, the selection component 1908 may determine a time at whichcommunication through the second serving beam corresponding to the atleast one beam index is to occur. In one aspect, the time may correspondto a symbol or a subframe. The selection component 1908 may determinethe time and instruct the communication component 1912 to switch to thesecond serving beam at the determined time.

In one aspect, the selection component 1908 may determine the time basedon the beam modification command. For example, the selection component1908 may determine, based on inclusion of the beam modification commandin a MAC CE, to switch communication through the first serving beam tothe second serving beam at the beginning of a subframen+k_(beamswitch-delay-mac), where n is the subframe used for HARQ-ACKtransmission associated with the MAC CE and k_(beamswitch-delay-mac) isequal to 14.

According to another example, based on inclusion of the beammodification command in a DCI message, the selection component 1908 maydetermine to switch from the first serving beam to the second servingbeam at the beginning of a subframe n+k_(beamswitch-delay-dic), where nis the subframe used for transmission of a BSI report andk_(beamswitch-delay-dic) is equal to 11.

In an aspect, the selection component 1908 may receive a beammodification command indicating that the first serving beam is not to beswitched. For example, a beam modification command may include a beamswitch indication field having a predetermined value (e.g., “0”) fromwhich the selection component 1908 may determine that the first servingbeam used by the communication component 1912 is not to be switched.Accordingly, the selection component 1908 may instruct the communicationcomponent 1912 to continue communication through the first serving beam,or the selection component 1908 may refrain from providing beam indexand/or channel information to the communication component 1912.

Based on instruction from the selection component 1908, thecommunication component 1912 may communicate with the base station 1950through the at least one beam corresponding to the at least one beamindex. In other words, the communication component 1912 may communicatewith the base station 1950 through the second serving beam on or morechannels, rather than communicate with the base station 1950 through thefirst serving beam.

In an aspect, the communication component 1912 may communicate with thebase station 1950 through the second serving beam on one or morechannels indicated by the selection component 1908. For example, thecommunication component 1912 may communicate with the base station 1950through the second serving beam on one or more uplink channels or one ormore downlink channels.

The apparatus may include additional components that perform each of theblocks of the algorithm in the aforementioned flowcharts of FIG. 12. Assuch, each block in the aforementioned flowcharts of FIG. 12 may beperformed by a component and the apparatus may include one or more ofthose components. The components may be one or more hardware componentsspecifically configured to carry out the stated processes/algorithm,implemented by a processor configured to perform the statedprocesses/algorithm, stored within a computer-readable medium forimplementation by a processor, or some combination thereof.

FIG. 20 is a diagram 2000 illustrating an example of a hardwareimplementation for an apparatus 1902′ employing a processing system2014. The processing system 2014 may be implemented with a busarchitecture, represented generally by the bus 2024. The bus 2024 mayinclude any number of interconnecting buses and bridges depending on thespecific application of the processing system 2014 and the overalldesign constraints. The bus 2024 links together various circuitsincluding one or more processors and/or hardware components, representedby the processor 2004, the components 1904, 1906, 1908, 1910, 1912, andthe computer-readable medium/memory 2006. The bus 2024 may also linkvarious other circuits such as timing sources, peripherals, voltageregulators, and power management circuits, which are well known in theart, and therefore, will not be described any further.

The processing system 2014 may be coupled to a transceiver 2010. Thetransceiver 2010 is coupled to one or more antennas 2020. Thetransceiver 2010 provides a means for communicating with various otherapparatus over a transmission medium. The transceiver 2010 receives asignal from the one or more antennas 2020, extracts information from thereceived signal, and provides the extracted information to theprocessing system 2014, specifically the reception component 1904. Inaddition, the transceiver 2010 receives information from the processingsystem 2014, specifically the transmission component 1910, and based onthe received information, generates a signal to be applied to the one ormore antennas 2020. The processing system 2014 includes a processor 2004coupled to a computer-readable medium/memory 2006. The processor 2004 isresponsible for general processing, including the execution of softwarestored on the computer-readable medium/memory 2006. The software, whenexecuted by the processor 2004, causes the processing system 2014 toperform the various functions described supra for any particularapparatus. The computer-readable medium/memory 2006 may also be used forstoring data that is manipulated by the processor 2004 when executingsoftware. The processing system 2014 further includes at least one ofthe components 1904, 1906, 1908, 1910, 1912. The components may besoftware components running in the processor 2004, resident/stored inthe computer readable medium/memory 2006, one or more hardwarecomponents coupled to the processor 2004, or some combination thereof.The processing system 2014 may be a component of the UE 350 and mayinclude the memory 360 and/or at least one of the TX processor 368, theRX processor 356, and the controller/processor 359.

In one configuration, the apparatus 1902/1902′ for wirelesscommunication includes means for receiving, from a base station, a beammodification command indicating at least one beam index forcommunicating through at least one beam on at least one channel, andeach beam index of the at least one beam index may indicate at least adirection for communicating through a corresponding beam of the at leastone beam. The apparatus 1902/1902′ may further include means forcommunicating, with the base station, through the at least one beamcorresponding to the at least one beam index on the at least onechannel.

In an aspect, the apparatus 1902/1902′ may further include means forcommunicating, with the base station, through a serving beamcorresponding to a serving beam index; The apparatus 1902/1902′ mayfurther include means for switching, after receiving the beammodification command, from the serving beam to the at least one beamcorresponding to the at least one beam index indicated by the beammodification command. In an aspect, the means for switching from theserving beam to the at least one beam is configured to switch from theserving beam to the at least one beam at a predetermined time. In anaspect, the predetermined time is associated with at least one of asymbol or subframe, and wherein the beam modification command indicatesthe at least one of the symbol or the subframe.

In an aspect, the beam modification command indicates, for each beamindex of the at least one beam index, a corresponding channel of the atleast one channel. In an aspect, the at least one beam index comprises aplurality of beam indexes, and the at least one channel comprises aplurality of channels. In an aspect, the at least one beam index isapplicable to one of uplink communication or downlink communication.

In an aspect, the beam modification command is received in a MAC CE. Inan aspect, the beam modification command is received in a DCI message.In an aspect, the apparatus 1902/1902′ may further include means fordetermining the at least one channel based on a DCI format of the DCImessage. In an aspect, the beam modification command is received via RRCsignaling.

The aforementioned means may be one or more of the aforementionedcomponents of the apparatus 1902 and/or the processing system 2014 ofthe apparatus 1902′ configured to perform the functions recited by theaforementioned means. As described supra, the processing system 2014 mayinclude the TX Processor 368, the RX Processor 356, and thecontroller/processor 359. As such, in one configuration, theaforementioned means may be the TX Processor 368, the RX Processor 356,and the controller/processor 359 configured to perform the functionsrecited by the aforementioned means.

FIG. 21 is a conceptual data flow diagram 2100 illustrating the dataflow between different means/components in an exemplary apparatus 2102.The apparatus may be a UE. The data flow illustrated in the diagram 2100is to be regarded as illustrative. Therefore, one or more additionalmeans/components may be present, and one or more illustratedmeans/components may be absent, according to various aspects. Further,various data flow may occur between means/components in addition toand/or instead of the illustrated data flow.

The apparatus 2102 may include a reception component 2104 configured toreceive signals from a base station (e.g., the base station 2150, a mmWbase station, an eNB, etc.). The apparatus 2102 may further include atransmission component 2110 configured to transmit signals to a basestation (e.g., the base station 2150, a mmW base station, an eNB, etc.).

In aspects, the reception component 2104 may receive, from the basestation 2150, through a set of beams a set of BRSs. Each BRS of the setof BRSs may correspond to a beam, and each beam may correspond to a beamindex (ergo, each BRS may correspond to a beam index). Each BRS may bereceived through a beam that may be used for communication between theapparatus 2102 and the base station 2150. The reception component 2104may provide the set of BRSs to a measurement component 2106.

The measurement component 2106 may be configured to measure a signalquality of each BRS of the set of received BRSs. For example, themeasurement component 2106 may measure at least one of a BRSRP, a BRSRQ,an SIR, an SINR, an SNR, or another value indicative of signal quality.

The measurement component 2106 may provide measurement information to acandidate component 2108. The candidate component 2108 may be configuredto maintain a set of candidate beam indexes corresponding to a set ofbest measured signal qualities of the set of BRSs. For example, the setof best measured signal qualities may be a set of the highest measuredsignal qualities.

In an aspect, the candidate component 2108 may be configured to maintainN candidate beam indexes in the set of candidate beam indexes. Thenumber N may be predetermined, for example, as defined by one or morestandards promulgated by 3GPP. For example, the candidate component 2108may maintain N=4 candidate beam indexes in the set of candidate beamindexes.

In an aspect, the candidate component 2108 may be configured to maintainthe set of best measured signal qualities of the set of BRSs based on amost recent set of signal qualities of the set of BRSs (e.g., the mostrecent measured signal qualities for the most recently received set ofBRSs). In another aspect, the candidate component 2108 may be configuredto maintain the set of best measured signal qualities of the set of BRSsbased on a filtered set of signal qualities of the set of BRSs. Inanother aspect, the candidate component 2108 may be configured tomaintain the set of best measured signal qualities of the set of BRSsbased on a time-averaged set of signal qualities of the set of BRSs.

In an aspect, the candidate component 2108 may be configured to maintainthe set of candidate beam indexes based on one or more criteria. Forexample, the candidate component 2108 may maintain the set of candidatebeam indexes based on one or more hysteresis criteria for including abeam index in or excluding a beam index from the set of candidate beamindexes.

In one aspect, the candidate component 2108 may be configured tomaintain the set of candidate beam indexes based on beam indexinformation received from the base station 2150. For example, thecandidate component 2108 may receive, from the base station 2150, anindication of one or more beam indexes that are to be excluded from themaintained set of candidate beam indexes. Accordingly, the candidatecomponent 2108 may exclude the indicated one or more beam indexes fromthe maintained set of candidate beam indexes.

In an aspect, the candidate component 2108 may be configured to providecandidate beam index information to a reporting component 2112 based onthe set of candidate beam indexes. For example, the candidate component2108 may select at least one best (e.g., highest) signal quality andprovide the best signal quality and corresponding candidate beam indexto the reporting component 2112. In an aspect, the candidate beam indexinformation may include at least a beam index and a signal qualitycorresponding to a beam through which the corresponding BRS is received.The reporting component 2112 may be configured to generate a BSI reportindicating at least the signal quality and the beam index correspondingto the at last one measured signal quality. The reporting component 2112may cause the transmission component 2110 to transmit the BSI report tothe base station 2150.

The apparatus may include additional components that perform each of theblocks of the algorithm in the aforementioned flowcharts of FIG. 13. Assuch, each block in the aforementioned flowcharts of FIG. 13 may beperformed by a component and the apparatus may include one or more ofthose components. The components may be one or more hardware componentsspecifically configured to carry out the stated processes/algorithm,implemented by a processor configured to perform the statedprocesses/algorithm, stored within a computer-readable medium forimplementation by a processor, or some combination thereof.

FIG. 22 is a diagram 2200 illustrating an example of a hardwareimplementation for an apparatus 2102′ employing a processing system2214. The processing system 2214 may be implemented with a busarchitecture, represented generally by the bus 2224. The bus 2224 mayinclude any number of interconnecting buses and bridges depending on thespecific application of the processing system 2214 and the overalldesign constraints. The bus 2224 links together various circuitsincluding one or more processors and/or hardware components, representedby the processor 2204, the components 2104, 2106, 2108, 2110, 2112 andthe computer-readable medium/memory 2206. The bus 2224 may also linkvarious other circuits such as timing sources, peripherals, voltageregulators, and power management circuits, which are well known in theart, and therefore, will not be described any further.

The processing system 2214 may be coupled to a transceiver 2210. Thetransceiver 2210 is coupled to one or more antennas 2220. Thetransceiver 2210 provides a means for communicating with various otherapparatus over a transmission medium. The transceiver 2210 receives asignal from the one or more antennas 2220, extracts information from thereceived signal, and provides the extracted information to theprocessing system 2214, specifically the reception component 2104. Inaddition, the transceiver 2210 receives information from the processingsystem 2214, specifically the transmission component 2110, and based onthe received information, generates a signal to be applied to the one ormore antennas 2220. The processing system 2214 includes a processor 2204coupled to a computer-readable medium/memory 2206. The processor 2204 isresponsible for general processing, including the execution of softwarestored on the computer-readable medium/memory 2206. The software, whenexecuted by the processor 2204, causes the processing system 2214 toperform the various functions described supra for any particularapparatus. The computer-readable medium/memory 2206 may also be used forstoring data that is manipulated by the processor 2204 when executingsoftware. The processing system 2214 further includes at least one ofthe components 2104, 2106, 2108. The components may be softwarecomponents running in the processor 2204, resident/stored in thecomputer readable medium/memory 2206, one or more hardware componentscoupled to the processor 2204, or some combination thereof. Theprocessing system 2214 may be a component of the UE 350 and may includethe memory 360 and/or at least one of the TX processor 368, the RXprocessor 356, and the controller/processor 359.

In one configuration, the apparatus 2102/2102′ for wirelesscommunication includes means for receiving, from a base station, througha set of beams a set of BRSs. The apparatus 2102/2102′ may furtherinclude means for measuring a signal quality of each BRS of the set ofBRSs, and each measured signal quality may correspond to a beam of theset of beams. In an aspect, the apparatus 2102/2102′ may include meansfor maintaining a set of candidate beam indexes corresponding to a setof best measured signal qualities of the set of BRSs.

The apparatus 2102/2102′ may further include means for transmitting, tothe base station, BSI indicating at least one measured signal qualityand at least one beam index from the set of maintained candidate beamindexes, the at least one beam index corresponding to the at least onemeasured signal quality. In an aspect, the set of the best measuredsignal qualities is a set of the highest measured signal qualities. Inan aspect, N candidate beam indexes are maintained in the set ofcandidate beam indexes, and N may be predetermined. In an aspect, theset of best measured signal qualities of the set of BRSs is based on amost recent set of signal qualities of the set of BRSs, a filtered setof signal qualities of the set of BRSs, or a time-averaged set of signalqualities of the set of BRSs. In an aspect, the maintenance of the setof candidate beam indexes is based on at least one hysteresis criteriafor including a beam index in or excluding a beam index from the set ofcandidate beam indexes. In an aspect, the apparatus 2102/2102′ mayfurther include means for receiving, from the base station, anindication of one or more beam indexes that are to be excluded from themaintained set of candidate beam indexes. In an aspect, the signalquality comprises at least one of a BRSRP, a BRSRQ, an SIR, an SNR, oran SINR.

The aforementioned means may be one or more of the aforementionedcomponents of the apparatus 2102 and/or the processing system 2214 ofthe apparatus 2102′ configured to perform the functions recited by theaforementioned means. As described supra, the processing system 2214 mayinclude the TX Processor 368, the RX Processor 356, and thecontroller/processor 359. As such, in one configuration, theaforementioned means may be the TX Processor 368, the RX Processor 356,and the controller/processor 359 configured to perform the functionsrecited by the aforementioned means.

FIG. 23 is a conceptual data flow diagram 2300 illustrating the dataflow between different means/components in an exemplary apparatus 2302.The apparatus may be a UE. The data flow illustrated in the diagram 2300is to be regarded as illustrative. Therefore, one or more additionalmeans/components may be present, and one or more illustratedmeans/components may be absent, according to various aspects. Further,various data flow may occur between means/components in addition toand/or instead of the illustrated data flow.

The apparatus 2302 may include a reception component 2304 configured toreceive signals from a base station (e.g., the base station 2350, a mmWbase station, an eNB, etc.). The apparatus 2302 may further include atransmission component 2310 configured to transmit signals to a basestation (e.g., the base station 2350, a mmW base station, an eNB, etc.).

In aspects, the reception component 2304 may receive, from the basestation 2350, a set of signals (e.g., a signal may be an aspect of aBRS) through a set of beams. Each signal of the set of signals maycorrespond to a beam, and each beam may correspond to a beam index(ergo, each signal may correspond to a beam index). Each signal may bereceived through a respective beam that may be used for communicationbetween the apparatus 2302 and the base station 2350. The receptioncomponent 2304 may provide the set of BRSs to a measurement component2306.

The measurement component 2306 may be configured to determine a receivedpower for each signal of the set of signals received through each beamof the set of beams. Each received power may be associated with a beamof the set of beams. For example, the measurement component 2306 maymeasure at least one of a BRSRP.

The measurement component 2306 may provide, to the reporting component2312, measurement information. The measurement information may includeone or more beam indexes and one or more received powers (e.g., a firstbeam index and a corresponding first received power, a second beam indexand a corresponding second received power, etc.).

In one aspect, the reporting component 2312 may be configured tomaintain a set of candidate beam indexes. The set of candidate beamindexes may include a predetermined number of candidate beam indexes(e.g., four candidate beam indexes) and a respective received power foreach BRS corresponding to each beam index of the predetermined number ofcandidate beam indexes. In an aspect, the set of candidate beam indexesmay include a set of beam indexes corresponding to the highest receivedpowers for a set of BRSs. The reporting component 2312 may sort the setof candidate beam indexes in decreasing order of highest received power,beginning with the beam index corresponding to the highest receivedpower.

The reporting component 2312 may be configured to generate one or moreBSI reports. The reporting component 2312 may generate a BSI report toinclude at least a beam index and a corresponding received power. Thereporting component 2312 may select a beam index and correspondingreceived power from the maintained set of candidate beam indexes. Thereporting component 2312 may be configured to cause the transmissioncomponent 2310 to send one or more BSI reports to the base station 2350.The number N of BSI reports to transmit to the base station 2350 may bedetermined by the determination component 2308. Additionally, thedetermination component 2308 may determine a channel that is to carrythe one or more BSI reports, and indicate the determined channel to thereporting component 2312 so that the one or more BSI reports are carriedon the determined channel.

According to aspects, the determination component 2308 may determine thenumber N of BSI reports to send to the base station 2350 based on amessage requesting BSI. For example, the determination component 2308may determine the number N based on a type of the message received fromthe base station 2350.

In an aspect, the type of message requesting BSI may be a DCI message(e.g., a downlink DCI message). The determination component 2308 maydetermine that the number N of BSI reports to send to the base station2350 is one when the message requesting BSI is indicated by a DCImessage (e.g., a downlink DCI message). In an aspect, the determinationcomponent 2308 may determine that the one BSI report is to be carried ona PUCCH (e.g., an ePUCCH).

In another aspect, the determination component 2308 may determine thatthe number N of BSI reports to send to the base station 2350 isdifferent from one when the message requesting BSI is indicated by anuplink DCI message. For example, the determination component 2308 maydetermine that the number N is zero, two, or four based on an indicationincluded in the uplink DCI message. When the determination component2308 determines that the number N is greater than one (e.g., two orfour), the determination component 2308 may determine that the BSIreports are to be carried on a PUSCH (e.g., an ePUSCH).

In another aspect, the type of message requesting BSI may be an RARmessage (e.g., a MSG2, an uplink grant associated with a RACH procedure,etc.). The determination component 2308 may determine that the number Nof BSI reports to send to the base station 2350 is different from onewhen the message requesting BSI is indicated by an RAR message. Forexample, the determination component 2308 may determine that the numberN is zero, two, or four based on an indication included in the RARmessage. When the determination component 2308 determines that thenumber N is greater than one (e.g., two or four), the determinationcomponent 2308 may determine that the BSI reports are to be carried on aPUSCH (e.g., an ePUSCH).

The determination component 2308 may indicate, to the reportingcomponent 2312, the number N and/or the channel on which the BSIreport(s) are to be carried. As described, the reporting component 2312may cause the transmission component 2310 to send, to the base station2350, the N BSI report(s) on the indicated channel.

The apparatus may include additional components that perform each of theblocks of the algorithm in the aforementioned flowcharts of FIG. 14. Assuch, each block in the aforementioned flowcharts of FIG. 14 may beperformed by a component and the apparatus may include one or more ofthose components. The components may be one or more hardware componentsspecifically configured to carry out the stated processes/algorithm,implemented by a processor configured to perform the statedprocesses/algorithm, stored within a computer-readable medium forimplementation by a processor, or some combination thereof.

FIG. 24 is a diagram 2400 illustrating an example of a hardwareimplementation for an apparatus 2302′ employing a processing system2414. The processing system 2414 may be implemented with a busarchitecture, represented generally by the bus 2424. The bus 2424 mayinclude any number of interconnecting buses and bridges depending on thespecific application of the processing system 2414 and the overalldesign constraints. The bus 2424 links together various circuitsincluding one or more processors and/or hardware components, representedby the processor 2404, the components 2304, 2306, 2308, 2310, 2312 andthe computer-readable medium/memory 2406. The bus 2424 may also linkvarious other circuits such as timing sources, peripherals, voltageregulators, and power management circuits, which are well known in theart, and therefore, will not be described any further.

The processing system 2414 may be coupled to a transceiver 2410. Thetransceiver 2410 is coupled to one or more antennas 2420. Thetransceiver 2410 provides a means for communicating with various otherapparatus over a transmission medium. The transceiver 2410 receives asignal from the one or more antennas 2420, extracts information from thereceived signal, and provides the extracted information to theprocessing system 2414, specifically the reception component 2304. Inaddition, the transceiver 2410 receives information from the processingsystem 2414, specifically the transmission component 2310, and based onthe received information, generates a signal to be applied to the one ormore antennas 2420. The processing system 2414 includes a processor 2404coupled to a computer-readable medium/memory 2406. The processor 2404 isresponsible for general processing, including the execution of softwarestored on the computer-readable medium/memory 2406. The software, whenexecuted by the processor 2404, causes the processing system 2414 toperform the various functions described supra for any particularapparatus. The computer-readable medium/memory 2406 may also be used forstoring data that is manipulated by the processor 2404 when executingsoftware. The processing system 2414 further includes at least one ofthe components 2304, 2306, 2308, 2310, 2312. The components may besoftware components running in the processor 2404, resident/stored inthe computer readable medium/memory 2406, one or more hardwarecomponents coupled to the processor 2404, or some combination thereof.The processing system 2414 may be a component of the UE 350 and mayinclude the memory 360 and/or at least one of the TX processor 368, theRX processor 356, and the controller/processor 359.

In one configuration, the apparatus 2302/2302′ for wirelesscommunication includes means for receiving, from a base station, amessage requesting BSI. The apparatus 2302/2302′ may further includemeans for determining a number N of BSI reports to send to the basestation, each BSI report indicating a beam index corresponding to a beamand a received power associated with the beam. The apparatus 2302/2302′may further include means for sending, to the base station, N BSIreports based on the message requesting BSI.

In an aspect, the apparatus 2302/2302′ may further include means forreceiving, from the base station, a set of signals through a set ofbeams. The apparatus 2302/2302′ may further include means fordetermining the received power for each signal of the set of signalsreceived through each beam of the set of beams, each received powerassociated with a beam of the set of beams.

In an aspect, the N BSI reports include N received powers correspondingto the highest determined received powers. In an aspect, thedetermination of the number N of BSI reports to send to the base stationis based on a type of the message requesting the BSI. In an aspect, thetype of the message requesting the BSI comprises a DCI message. In anaspect, the number N of BSI reports to send to the base station isdetermined to be one based on the DCI message. In an aspect, thedetermined number N of BSI reports are sent on a PUCCH. In an aspect,the type of message requesting the BSI comprises an RAR message. In anaspect, the number N of BSI reports is determined to be greater than onebased on the RAR message. In an aspect, the determined number N of BSIreports are sent on a PUSCH.

The aforementioned means may be one or more of the aforementionedcomponents of the apparatus 2302 and/or the processing system 2414 ofthe apparatus 2302′ configured to perform the functions recited by theaforementioned means. As described supra, the processing system 2414 mayinclude the TX Processor 368, the RX Processor 356, and thecontroller/processor 359. As such, in one configuration, theaforementioned means may be the TX Processor 368, the RX Processor 356,and the controller/processor 359 configured to perform the functionsrecited by the aforementioned means.

FIG. 25 is a conceptual data flow diagram 2500 illustrating the dataflow between different means/components in an exemplary apparatus 2502.The apparatus may be a UE. The data flow illustrated in the diagram 2500is to be regarded as illustrative. Therefore, one or more additionalmeans/components may be present, and one or more illustratedmeans/components may be absent, according to various aspects. Further,various data flow may occur between means/components in addition toand/or instead of the illustrated data flow.

The apparatus 2502 may include a reception component 2504 configured toreceive signals from a base station (e.g., the base station 2550, a mmWbase station, an eNB, etc.). The apparatus 2502 may further include atransmission component 2510 configured to transmit signals to a basestation (e.g., the base station 2550, a mmW base station, an eNB, etc.).

In an aspect, the apparatus 2502 may include a selection component 2506.The selection component 2506 may be configured to select a first beamfor communication with the base station 2550. For example, the selectioncomponent 2506 may select the first beam based on an estimation ordetermination of a beam through which the selection component 2506expects the base station 2550 to be able to receive signals from theapparatus 2502.

In one aspect, the selection component 2506 may select the first beambased on reception of one or more BRSs from the base station 2550. Theselection component 2506 may select a beam corresponding to a BRS with ahighest received power or quality (e.g., a highest BRSRP). For example,the selection component 2506 may determine a beam index corresponding toa BRS with a highest received power or quality and select a beamcorresponding to that beam index. The selection component 2506 mayprovide, to a RACH component 2508, an indication of the selected firstbeam (e.g., a first beam index corresponding to the selected firstbeam).

The RACH component 2508 may be configured to perform a RACH procedurewith the base station 2550. For example, the RACH component 2508 maydetermine that a RACH procedure is successful when the RACH component2508 receives, from the base station 2550, a contention resolutionmessage (e.g., a MSG4) and/or when the RACH component 2508 causes theapparatus 2502 to be synchronized with a network that includes the basestation 2550.

In an aspect, the RACH component 2508 may perform a RACH procedure thatincludes communication of a plurality of RACH messages between theapparatus 2502 and the base station 2550. For example, the RACHprocedure may include transmission of a random access preamble (e.g., aMSG1) to the base station 2550, reception of an RAR message (e.g., aMSG2) from the base station 2550 based on the random access preamble,transmission of a connection request message (e.g., a MSG3) to the basestation 2550 based on the RAR message, and reception of a contentionresolution message (e.g., a MSG4) from the base station 2550 based onthe connection request message.

The RACH component 2508 may be configured to determine that a RACHprocedure with the base station 2550 failed. For example, if the RACHcomponent 2508 fails to receive and/or decode an RAR message or acontention resolution message, then the RACH component 2508 maydetermine that the RACH procedure with the base station 2550 has failed.

In an aspect, the RACH component 2508 may attempt, through the selectedfirst beam, at least one RACH procedure. For example, the RACH component2508 may cause the transmission component 2510 to send, through theselected first beam, a random access preamble. Additionally, the RACHcomponent 2508 may cause the transmission component 2510 to send,through the selected first beam, a connection request message based onan RAR message.

In an aspect, the RACH component 2508 may determine that the at leastone RACH procedure with the base station 2550 has failed. For example,the RACH component 2508 may fail to receive and/or decode an RAR messageor a contention resolution message. The RACH component 2508 may provideinformation indicating the at least one RACH procedure failed to theselection component 2506 and/or a maintenance component 2512.

According to an aspect, the information indicating that the at least oneRACH procedure failed may include information associated with theselected first beam (e.g., a first beam index corresponding to theselected first beam). According to an aspect, the information indicatingthat the at least one RACH procedure failed may include informationindicating a subframe in which a RACH message associated with the RACHprocedure is carried.

In one aspect, the selection component 2506 may select a new beam forcommunication with the base station 2550 based on the informationindicating that the at least one RACH procedure failed. In anotheraspect, the selection component 2506 may determine an increasedtransmission power for transmission of RACH messages based on theinformation indicating that the at least one RACH procedure failed. Theselection component 2506 may indicate, to the RACH component 2508, thenew beam (e.g., a new beam index corresponding to the new beam) and/orthe increased transmission power.

Accordingly, the RACH component 2508 may attempt a next RACH procedurethrough the new beam and/or using the increased transmission power. Whennext RACH procedure is successful, the RACH component 2508 may indicate,to the maintenance component 2512, that the next RACH procedure with thebase station 2550 succeeded.

In an aspect, the maintenance component 2512 may store the informationindicating that the at least one RACH procedure failed. For example, themaintenance component 2512 may store information associated with theselected first beam (e.g., a first beam index corresponding to theselected first beam).

In one aspect, the maintenance component 2512 may be configured tomaintain a set of candidate beam indexes. The set of candidate beamindexes may include a predetermined number of candidate beam indexes(e.g., four candidate beam indexes) and a respective received power foreach BRS corresponding to each beam index of the predetermined number ofcandidate beam indexes. In an aspect, the set of candidate beam indexesmay include a set of beam indexes corresponding to the BRSs having thehighest received powers. The maintenance component 2512 may sort the setof candidate beam indexes in decreasing order of highest received power,beginning with the beam index corresponding to the highest receivedpower. In an aspect, the maintenance component 2512 may be configured toexclude, from the set of candidate beam indexes, the first beam indexcorresponding to the selected first beam.

When the next RACH procedure with the base station 2550 succeeds, themaintenance component 2512 may send, to the base station 2550,information indicating that the at least one RACH procedure failed. Inan aspect, the information indicating that the at least one RACHprocedure failed may include information associated with the selectedfirst beam (e.g., a first beam index corresponding to the selected firstbeam). In another aspect, the information indicating that the at leastone RACH procedure failed may include an indication of a subframe inwhich a RACH message associated with the at least one RACH procedure iscarried. For example, the information may indicate a subframe in which arandom access preamble is carried or a subframe in which a connectionrequest message is carried.

In one aspect, the maintenance component 2512 may generate a BSI report.The maintenance component 2512 may generate the BSI report to indicatethe information associated with the at least failed RACH procedure(e.g., a first beam index corresponding to the selected first beam). Themaintenance component 2512 may cause the transmission component 2510 tosend the BSI report to the base station 2550, for example, through thenew beam associated with the successful RACH procedure.

The apparatus may include additional components that perform each of theblocks of the algorithm in the aforementioned flowcharts of FIG. 15. Assuch, each block in the aforementioned flowcharts of FIG. 15 may beperformed by a component and the apparatus may include one or more ofthose components. The components may be one or more hardware componentsspecifically configured to carry out the stated processes/algorithm,implemented by a processor configured to perform the statedprocesses/algorithm, stored within a computer-readable medium forimplementation by a processor, or some combination thereof.

FIG. 26 is a diagram 2600 illustrating an example of a hardwareimplementation for an apparatus 2502′ employing a processing system2614. The processing system 2614 may be implemented with a busarchitecture, represented generally by the bus 2624. The bus 2624 mayinclude any number of interconnecting buses and bridges depending on thespecific application of the processing system 2614 and the overalldesign constraints. The bus 2624 links together various circuitsincluding one or more processors and/or hardware components, representedby the processor 2604, the components 2504, 2506, 2508, 2510, 2512 andthe computer-readable medium/memory 2606. The bus 2624 may also linkvarious other circuits such as timing sources, peripherals, voltageregulators, and power management circuits, which are well known in theart, and therefore, will not be described any further.

The processing system 2614 may be coupled to a transceiver 2610. Thetransceiver 2610 is coupled to one or more antennas 2620. Thetransceiver 2610 provides a means for communicating with various otherapparatus over a transmission medium. The transceiver 2610 receives asignal from the one or more antennas 2620, extracts information from thereceived signal, and provides the extracted information to theprocessing system 2614, specifically the reception component 2504. Inaddition, the transceiver 2610 receives information from the processingsystem 2614, specifically the transmission component 2510, and based onthe received information, generates a signal to be applied to the one ormore antennas 2620. The processing system 2614 includes a processor 2604coupled to a computer-readable medium/memory 2606. The processor 2604 isresponsible for general processing, including the execution of softwarestored on the computer-readable medium/memory 2606. The software, whenexecuted by the processor 2604, causes the processing system 2614 toperform the various functions described supra for any particularapparatus. The computer-readable medium/memory 2606 may also be used forstoring data that is manipulated by the processor 2604 when executingsoftware. The processing system 2614 further includes at least one ofthe components 2504, 2506, 2508, 2510, 2512. The components may besoftware components running in the processor 2604, resident/stored inthe computer readable medium/memory 2606, one or more hardwarecomponents coupled to the processor 2604, or some combination thereof.The processing system 2614 may be a component of the UE 350 and mayinclude the memory 360 and/or at least one of the TX processor 368, theRX processor 356, and the controller/processor 359.

In one configuration, the apparatus 2502/2502′ for wirelesscommunication includes means for selecting a first beam forcommunication with a base station. The apparatus 2502/2502′ may furtherinclude means for attempting, through the selected first beam, at leastone RACH procedure with the base station. The apparatus 2502/2502′ mayfurther include means for determining that the at least one RACHprocedure failed with the base station. The apparatus 2502/2502′ mayfurther include means for sending, after a successful RACH procedurewith the base station, information indicating that the at least one RACHprocedure failed.

In an aspect, the apparatus 2502/2502′ may further include means forselecting a new beam for communication with the base station after thedetermination that the at least one RACH procedure failed. In an aspect,at least a portion of the successful RACH procedure is performed throughthe selected new beam.

In an aspect, the apparatus 2502/2502′ may further include means forincreasing a transmission power after the determination that the atleast one RACH procedure failed. In an aspect, at least a portion of thesuccessful RACH procedure is performed with the increased transmissionpower.

In an aspect, the apparatus 2502/2502′ may further include means forstoring information associated with the selected first beam based on thedetermination that the at least one RACH procedure failed. In an aspect,the information indicating that the at least one RACH procedure failedincludes the stored information associated with the first beam. In anaspect, the information indicating that the at least one RACH procedurefailed includes an indication of a subframe in which a RACH messageassociated with the at least one RACH procedure is carried.

In an aspect, the apparatus 2502/2502′ may further include means forexcluding the selected first beam from a candidate beam set maintainedby the apparatus based on the determination that the at least one RACHprocedure failed.

In an aspect, the information indicating that the at least one RACHprocedure failed comprises a BSI report. In an aspect, the means forattempting the at least one RACH procedure is configured to at least oneof: transmit, to the base station, a random access preamble; receive,from the base station, a random access response based on the randomaccess preamble; transmit, to the base station, a connection requestmessage based on the random access response; or receive a contentionresolution message based on the connection request message. In anaspect, the apparatus 2502/2502′ is synchronized with a network thatincludes the base station based on the successful RACH procedure.

The aforementioned means may be one or more of the aforementionedcomponents of the apparatus 2502 and/or the processing system 2614 ofthe apparatus 2502′ configured to perform the functions recited by theaforementioned means. As described supra, the processing system 2614 mayinclude the TX Processor 368, the RX Processor 356, and thecontroller/processor 359. As such, in one configuration, theaforementioned means may be the TX Processor 368, the RX Processor 356,and the controller/processor 359 configured to perform the functionsrecited by the aforementioned means.

FIG. 27 is a conceptual data flow diagram 2700 illustrating the dataflow between different means/components in an exemplary apparatus 2702.The apparatus may be a UE. The data flow illustrated in the diagram 2700is to be regarded as illustrative. Therefore, one or more additionalmeans/components may be present, and one or more illustratedmeans/components may be absent, according to various aspects. Further,various data flow may occur between means/components in addition toand/or instead of the illustrated data flow.

The apparatus 2702 may include a reception component 2704 configured toreceive signals from a base station (e.g., the base station 2750, a mmWbase station, an eNB, etc.). The apparatus 2702 may further include atransmission component 2710 configured to transmit signals to a basestation (e.g., the base station 2750, a mmW base station, an eNB, etc.).

The apparatus 2702 may include a RACH component 2708 that may beconfigured to perform a RACH procedure with the base station 2750. In anaspect, the RACH component 2708 may perform a RACH procedure thatincludes communication of a plurality of RACH messages between theapparatus 2702 and the base station 2750. For example, the RACHprocedure may include transmission of a random access preamble (e.g., aMSG1) to the base station 2750, reception of an RAR message (e.g., aMSG2) from the base station 2750 based on the random access preamble,transmission of a connection request message (e.g., a MSG3) to the basestation 2750 based on the RAR message, and reception of a contentionresolution message (e.g., a MSG4) from the base station 2750 based onthe connection request message.

In an aspect, the RACH component 2708 may provide a contentionresolution message (e.g., a MSG4) to a selection component 2706. Theselection component 2706 may be configured to select a new beam forcommunication with the base station 2750 based on the informationincluded in the contention resolution message.

The selection component 2706 may be configured to determine whether abeam index included in the contention resolution message is applicableto the apparatus 2702, and the beam index may be indicated by thecontention resolution message. In one aspect, the selection component2706 may determine whether the beam index included in the contentionresolution message is intended for the apparatus 2702. For example, theselection component 2706 may attempt to decode the contention resolutionmessage based on an RNTI associated with the apparatus 2702 (e.g., anRNTI determined as part of a RACH procedure). The selection component2706 may determine that the beam index included in the contentionresolution message is applicable to the apparatus 2702 when theselection component 2706 successfully decodes the contention resolutionmessage.

In an aspect, the selection component 2706 may provide an indication ofthe beam index to the reception component 2704 and/or the transmissioncomponent 2710. Therefore, the reception component 2704 and/or thetransmission component 2710 may communicate with the base station 2750through the beam corresponding to the beam index.

In an aspect, the selection component 2706 may determine one or morechannels associated with the beam index, for example, as indicated bythe contention resolution message. The selection component 2706 mayprovide an indication of the one or more channels to the receptioncomponent 2704 (e.g., for downlink channels) and/or the transmissioncomponent 2710 (e.g., for uplink channels). The reception component 2704and/or the transmission component 2710 may then communicate with thebase station 2750 through the beam corresponding to the beam index onthe one or more indicated channels.

In an aspect, the selection component 2706 may provide an indication ofwhether the beam index is applicable to the apparatus 2702 to anacknowledgement component 2712. The acknowledgement component 2712 maybe configured to determine whether to transmit feedback (e.g.,acknowledgement/non-acknowledgement feedback) to the base station 2750.In an aspect, when the selection component 2706 indicates to theacknowledgement component 2712 that the beam index is applicable to theapparatus 2702, the acknowledgement component 2712 may generate anacknowledgement message and cause the transmission component 2710 totransmit the acknowledgement message to the base station 2750. In anaspect, when the selection component 2706 indicates to theacknowledgement component 2712 that the beam index is inapplicable tothe apparatus 2702 or when the selection component 2706 indicates thatthe selection component 2706 is unable to successfully decode thecontention resolution message, the acknowledgement component 2712 mayrefrain from sending a non-acknowledgment message to the base station2750.

The apparatus may include additional components that perform each of theblocks of the algorithm in the aforementioned flowcharts of FIG. 16. Assuch, each block in the aforementioned flowcharts of FIG. 16 may beperformed by a component and the apparatus may include one or more ofthose components. The components may be one or more hardware componentsspecifically configured to carry out the stated processes/algorithm,implemented by a processor configured to perform the statedprocesses/algorithm, stored within a computer-readable medium forimplementation by a processor, or some combination thereof.

FIG. 28 is a diagram 2800 illustrating an example of a hardwareimplementation for an apparatus 2702′ employing a processing system2814. The processing system 2814 may be implemented with a busarchitecture, represented generally by the bus 2824. The bus 2824 mayinclude any number of interconnecting buses and bridges depending on thespecific application of the processing system 2814 and the overalldesign constraints. The bus 2824 links together various circuitsincluding one or more processors and/or hardware components, representedby the processor 2804, the components 2704, 2706, 2708, 2710, 2712 andthe computer-readable medium/memory 2806. The bus 2824 may also linkvarious other circuits such as timing sources, peripherals, voltageregulators, and power management circuits, which are well known in theart, and therefore, will not be described any further.

The processing system 2814 may be coupled to a transceiver 2810. Thetransceiver 2810 is coupled to one or more antennas 2820. Thetransceiver 2810 provides a means for communicating with various otherapparatus over a transmission medium. The transceiver 2810 receives asignal from the one or more antennas 2820, extracts information from thereceived signal, and provides the extracted information to theprocessing system 2814, specifically the reception component 2704. Inaddition, the transceiver 2810 receives information from the processingsystem 2814, specifically the transmission component 2710, and based onthe received information, generates a signal to be applied to the one ormore antennas 2820. The processing system 2814 includes a processor 2804coupled to a computer-readable medium/memory 2806. The processor 2804 isresponsible for general processing, including the execution of softwarestored on the computer-readable medium/memory 2806. The software, whenexecuted by the processor 2804, causes the processing system 2814 toperform the various functions described supra for any particularapparatus. The computer-readable medium/memory 2806 may also be used forstoring data that is manipulated by the processor 2804 when executingsoftware. The processing system 2814 further includes at least one ofthe components 2704, 2706, 2708, 2710, 2712. The components may besoftware components running in the processor 2804, resident/stored inthe computer readable medium/memory 2806, one or more hardwarecomponents coupled to the processor 2804, or some combination thereof.The processing system 2814 may be a component of the UE 350 and mayinclude the memory 360 and/or at least one of the TX processor 368, theRX processor 356, and the controller/processor 359.

In one configuration, the apparatus 2702/2702′ for wirelesscommunication includes means for receiving, from a base station, acontention resolution message, the contention resolution messageindicating at least a beam index corresponding to a beam. The apparatus2702/2702′ may further include means for determining whether the beamindex is applicable to the apparatus 2702/2702′. The apparatus2702/2702′ may further include means for communicating with the basestation through the beam corresponding to the beam index when the beamindex is applicable to the apparatus 2702/2702′.

In an aspect, the apparatus 2702/2702′ may further include means fortransmitting, to the base station, an acknowledgement message when thebeam index is determined to be applicable to the apparatus 2702/2702′.In an aspect, the contention resolution message is associated with arandom access procedure. In an aspect, the means for determining whetherthe beam index is applicable to the apparatus 2702/2702′ is configuredto attempt to decode the contention resolution message based on a RNTIassociated with the apparatus 2702/2702′, and the beam index isdetermined to be applicable to the apparatus 2702/2702′ when thecontention resolution message is successfully decoded.

In an aspect, the apparatus 2702/2702′ further includes means forrefraining from transmitting a non-acknowledgement message to the basestation when the beam index is determined to be inapplicable to theapparatus 2702/2702′ or if the contention resolution message isunsuccessfully decoded. In an aspect, the contention resolution messagefurther includes an indication of one or more channels associated withthe beam index, and the communication with the base station through thebeam corresponding to the beam index is performed on the one or moreindicated channels.

In an aspect, the apparatus 2702/2702′ further includes means fortransmitting, to the base station, a random access preamble. Theapparatus 2702/2702′ further includes means for receiving, from the basestation, a random access response based on the random access preamble.The apparatus 2702/2702′ further includes means for transmitting, to thebase station, a connection request message based on the random accessresponse. In an aspect, the contention resolution message is transmittedbased on the connection request message.

The aforementioned means may be one or more of the aforementionedcomponents of the apparatus 2702 and/or the processing system 2814 ofthe apparatus 2702′ configured to perform the functions recited by theaforementioned means. As described supra, the processing system 2814 mayinclude the TX Processor 368, the RX Processor 356, and thecontroller/processor 359. As such, in one configuration, theaforementioned means may be the TX Processor 368, the RX Processor 356,and the controller/processor 359 configured to perform the functionsrecited by the aforementioned means.

FIG. 29 is a conceptual data flow diagram 2900 illustrating the dataflow between different means/components in an exemplary apparatus 2902.The apparatus may be a base station. The data flow illustrated in thediagram 2900 is to be regarded as illustrative. Therefore, one or moreadditional means/components may be present, and one or more illustratedmeans/components may be absent, according to various aspects. Further,various data flow may occur between means/components in addition toand/or instead of the illustrated data flow.

The apparatus 2902 may include a reception component 2904 configured toreceive signals from a UE (e.g., the UE 2950, a mmW UE, etc.). Theapparatus 2902 may further include a transmission component 2910configured to transmit signals to a UE (e.g., the UE 2950, a mmW UE,etc.).

The apparatus 2902 may include a RACH component 2908 that may beconfigured to perform a RACH procedure with the UE 2950. In an aspect,the RACH component 2908 may perform a RACH procedure that includescommunication of a plurality of RACH messages between the apparatus 2902and the UE 2950. For example, the RACH procedure may include receptionof a random access preamble (e.g., a MSG1) from the UE 2950,transmission of an RAR message (e.g., a MSG2) to the UE 2950 based onthe random access preamble, reception of a connection request message(e.g., a MSG3) from the UE 2950 based on the RAR message, andtransmission of a contention resolution message (e.g., a MSG4) to the UE2950 based on the connection request message.

In an aspect, a selection component 2906 may be configured to determinea beam index applicable to the UE 2950, such as a beam index to be usedfor communication between the apparatus 2902 and the UE 2950. In oneaspect, the selection component 2906 may be configured to determine thebeam index based on feedback from the UE 2950 (e.g., feedback based onone or more BRSs transmitted by the apparatus 2902). The selectioncomponent 2906 may provide the beam index to the RACH component 2908.

In an aspect, the selection component 2906 may determine one or morechannels associated with the beam index, for example, to be indicated bythe contention resolution message. The selection component 2906 mayprovide an indication of the one or more channels to the RACH component2908 (e.g., for inclusion in a contention resolution message).

The RACH component 2908 may be configured to include, in a contentionresolution message, an indication of the beam index (and, optionally, anindication of one or more channels). In an aspect, the RACH component2908 may indicate that the beam index is applicable to the UE 2950. Forexample, the RACH component 2908 may scramble the contention resolutionmessage based on an RNTI associated with the UE 2950 (e.g., an RNTIdetermined as part of a RACH procedure). The RACH component 2908 maycause transmission, to the UE 2950, of the contention resolution messageindicating the beam index corresponding to the beam and indicating thatthe beam index is applicable to the UE 2950.

An acknowledgement component 2912 may be configured to determine whetherto feedback (e.g., acknowledgement/non-acknowledgement feedback) isreceived from the UE 2950. In an aspect, the acknowledgement component2912 may receive an acknowledgement message from the UE 2950, which mayindicate that the UE 2950 acknowledges that communication between theapparatus 2902 and the UE 2950 is to occur on the beam corresponding tothe beam index indicated by the contention resolution message. Theacknowledgement component 2912 may provide an indication of the beamindex to the reception component 2904 and/or the transmission component2910 (e.g., based on one or more channels on which communication is tooccur). The reception component 2904 and/or the transmission component2910 may then communicate with the UE 2950 through the beamcorresponding to the beam index on the one or more channels.

If the acknowledgement component 2912 does not receive anacknowledgement message, communication with the UE 2950 may occurthrough a serving beam that is used for communication beforetransmission of the contention resolution message.

The apparatus may include additional components that perform each of theblocks of the algorithm in the aforementioned flowcharts of FIG. 17. Assuch, each block in the aforementioned flowcharts of FIG. 17 may beperformed by a component and the apparatus may include one or more ofthose components. The components may be one or more hardware componentsspecifically configured to carry out the stated processes/algorithm,implemented by a processor configured to perform the statedprocesses/algorithm, stored within a computer-readable medium forimplementation by a processor, or some combination thereof.

FIG. 30 is a diagram 3000 illustrating an example of a hardwareimplementation for an apparatus 2902′ employing a processing system3014. The processing system 3014 may be implemented with a busarchitecture, represented generally by the bus 3024. The bus 3024 mayinclude any number of interconnecting buses and bridges depending on thespecific application of the processing system 3014 and the overalldesign constraints. The bus 3024 links together various circuitsincluding one or more processors and/or hardware components, representedby the processor 3004, the components 2904, 2906, 2908, 2910, 2912 andthe computer-readable medium/memory 3006. The bus 3024 may also linkvarious other circuits such as timing sources, peripherals, voltageregulators, and power management circuits, which are well known in theart, and therefore, will not be described any further.

The processing system 3014 may be coupled to a transceiver 3010. Thetransceiver 3010 is coupled to one or more antennas 3020. Thetransceiver 3010 provides a means for communicating with various otherapparatus over a transmission medium. The transceiver 3010 receives asignal from the one or more antennas 3020, extracts information from thereceived signal, and provides the extracted information to theprocessing system 3014, specifically the reception component 2904. Inaddition, the transceiver 3010 receives information from the processingsystem 3014, specifically the transmission component 2910, and based onthe received information, generates a signal to be applied to the one ormore antennas 3020. The processing system 3014 includes a processor 3004coupled to a computer-readable medium/memory 3006. The processor 3004 isresponsible for general processing, including the execution of softwarestored on the computer-readable medium/memory 3006. The software, whenexecuted by the processor 3004, causes the processing system 3014 toperform the various functions described supra for any particularapparatus. The computer-readable medium/memory 3006 may also be used forstoring data that is manipulated by the processor 3004 when executingsoftware. The processing system 3014 further includes at least one ofthe components 2904, 2906, 2908, 2910, 2912. The components may besoftware components running in the processor 3004, resident/stored inthe computer readable medium/memory 3006, one or more hardwarecomponents coupled to the processor 3004, or some combination thereof.The processing system 3014 may be a component of the base station 310and may include the memory 376 and/or at least one of the TX processor316, the RX processor 370, and the controller/processor 375.

In one configuration, the apparatus 2902/2902′ for wirelesscommunication includes means for means for transmitting, to a UE, acontention resolution message, the contention resolution messageindicating at least a beam index corresponding to a beam and indicatingthat the beam index is applicable to the UE. The apparatus 2902/2902′may further includes means for determining whether an acknowledgementmessage is received from the UE in response to the contention resolutionmessage. The apparatus 2902/2902′ may further include means forcommunicating with the UE through the beam corresponding to the beamindex when the acknowledgement message is determined to be received fromthe UE.

In an aspect, the contention resolution message is associated with arandom access procedure. In an aspect, the apparatus 2902/2902′ mayfurther include means for scrambling at least a portion of thecontention resolution message using an RNTI associated the UE. In anaspect, the contention resolution message further includes an indicationof one or more channels associated with the beam index, and thecommunication with the UE through the beam corresponding to the beamindex is performed on the one or more indicated channels.

In an aspect, the apparatus 2902/2902′ may further include means forcommunicating with the UE through a serving beam before transmission ofthe contention resolution message, and the communication with the UEcontinues through the serving beam based on an absence of anacknowledgement message from the UE.

In an aspect, the apparatus 2902/2902′ may further include means forreceiving, from the UE, a random access preamble. The apparatus2902/2902′ may further include means for transmitting, to the UE, arandom access response based on the random access preamble. Theapparatus 2902/2902′ may further include means for receiving, from theUE, a connection request message based on the random access response,and the contention resolution message is transmitted based on theconnection request message.

The aforementioned means may be one or more of the aforementionedcomponents of the apparatus 2902 and/or the processing system 3014 ofthe apparatus 2902′ configured to perform the functions recited by theaforementioned means. As described supra, the processing system 3014 mayinclude the TX Processor 316, the RX Processor 370, and thecontroller/processor 375. As such, in one configuration, theaforementioned means may be the TX Processor 316, the RX Processor 370,and the controller/processor 375 configured to perform the functionsrecited by the aforementioned means.

FIG. 31 is a conceptual data flow diagram 3100 illustrating the dataflow between different means/components in an exemplary apparatus 3102.The apparatus may be a UE. The data flow illustrated in the diagram 3100is to be regarded as illustrative. Therefore, one or more additionalmeans/components may be present, and one or more illustratedmeans/components may be absent, according to various aspects.

Further, various data flow may occur between means/components inaddition to and/or instead of the illustrated data flow.

The apparatus 3102 may include a reception component 3104 configured toreceive signals from a base station (e.g., the base station 3150, a mmWbase station, an eNB, etc.). The apparatus 3102 may further include atransmission component 3110 configured to transmit signals to a basestation (e.g., the base station 3150, a mmW base station, an eNB, etc.).

In aspects, the reception component 3104 may receive, from the basestation 3150, a set of signals (e.g., a signal may be an aspect of aBRS) through a set of beams. Each signal of the set of signals maycorrespond to a beam, and each beam may correspond to a beam index(ergo, each signal may correspond to a beam index). Each signal may bereceived through a respective beam that may be used for communicationbetween the apparatus 3102 and the base station 3150. The receptioncomponent 3104 may provide the set of BRSs to a command component 3106.The command component 3106 may determine transmit beam indexescorresponding to transmit beams of the base station 3150 based on arespective BRS received through a receptive transmit beam. The commandcomponent 3106 may provide the transmit beam indexes to a determinationcomponent 3108. The determination component 3108 may maintain a mappingof transmit beam indexes to receive beam indexes.

In various aspects, the command component 3106 may receive, through thereception component 3104 from the base station 3150, a beam modificationcommand. The beam modification command may indicate a set of transmitbeam indexes corresponding to a set of transmit beams of a base station,and each transmit beam index of the set of transmit beam indexes mayindicate at least a transmit direction for transmitting a transmit beamby the base station 3150. The command component 3106 may be configuredto determine the set of transmit beam indexes indicated by the beammodification command.

In an aspect, the beam modification command may be received in a MAC CE.In an aspect, the beam modification command may be received in a DCImessage. In an aspect, the beam modification command may be received viaRRC signaling. In an aspect, the beam modification command may becarried on a PDCCH.

In aspects, the command component 3106 may provide the set of transmitbeam indexes to a determination component 3108. The determinationcomponent 3108 may determine a set of receive beam indexes correspondingto a set of receive beams of the apparatus 3102 based on the set oftransmit beam indexes. Each receive beam index of the set of receivebeam indexes indicating at least a receive direction for receiving abeam by the apparatus 3102. In an aspect, the determination component3108 may determine the set of receive beam indexes by accessing amapping that maps transmit beam indexes to receive beam indexes. Thedetermination component 3108 and/or the command component 3106 may beconfigured to populate this mapping.

The determination component 3108 may provide the set of receive beamindexes to a BRRS component 3112. Accordingly, the BRRS component 3112may cause the reception component 3104 to receive through a receive beamcorresponding to a receive beam index included in the set of receivebeam indexes, for example, during a symbol in which a BRRS is to bereceived. In one aspect, the BRRS component 3112 may generate a receivebeam corresponding to the at least one receive beam index, for example,when the apparatus 3102 is not actively maintaining that beam.

In one aspect, the BRRS component 3112 may receive the BRRS through theset of transmit beams from the base station 3150 corresponding to theset of transmit beam indexes. In another aspect, the BRRS component 3112may receive the BRRS through a different set of transmit beam from thebase station 3150 than the set of transmit beams corresponding to thetransmit beam indexes indicated by the beam modification command. Forexample, obstruction and/or reflection may cause the apparatus 3102 toreceive the BRRS through the determined set of received beams, butthrough a different set of transmit beams than the set of transmit beamscorresponding to the set of transmit beam indexes indicated by the beammodification command.

In one aspect, the BRRS component 3112 may receive the BRRS in one ormore symbols corresponding to one or more symbol indexes. For example,the BRRS component 3112 may receive (e.g., listen) through the at leastone receive beam corresponding to the at least one receive beam indexduring one or more symbols corresponding to the one or more symbolindexes. In an aspect, the one or more symbol indexes may bepredetermined (e.g., defined by one or more standards promulgated by3GPP). In another aspect, the one or more symbol indexes may beindicated by the beam modification command (e.g., determined by thecommand component 3106 and provided to the BRRS component 3112). In oneaspect, the beam modification command further indicates a correspondingtransmit beam index of the set of transmit beam indexes for each symbolof the one or more symbol indexes.

In an aspect, the BRRS component 3112 may receive a first portion of theBRRS in a first set of symbols through a first receive beamcorresponding to a first receive beam index included in the determinedset of receive beam indexes. The BRRS component 3112 may receive asecond portion of the BRRS in a second set of symbols through a secondreceive beam corresponding to a second receive beam index included inthe determined set of receive beam indexes.

In one aspect, the BRRS component 3112 may generate a BRI report basedon one or more received BRRSs. In an aspect, the BRI report may besimilar to a BSI report, but may be used by the base station 3150 todetermine a best fine beam. The BRRS component 3112 may transmit a BRIreport to index a transmit beam index that is best (e.g., has a highestsignal quality or power based on a received BRRS).

The apparatus may include additional components that perform each of theblocks of the algorithm in the aforementioned flowcharts of FIG. 18. Assuch, each block in the aforementioned flowcharts of FIG. 18 may beperformed by a component and the apparatus may include one or more ofthose components. The components may be one or more hardware componentsspecifically configured to carry out the stated processes/algorithm,implemented by a processor configured to perform the statedprocesses/algorithm, stored within a computer-readable medium forimplementation by a processor, or some combination thereof.

FIG. 32 is a diagram 3200 illustrating an example of a hardwareimplementation for an apparatus 3102′ employing a processing system3214. The processing system 3214 may be implemented with a busarchitecture, represented generally by the bus 3224. The bus 3224 mayinclude any number of interconnecting buses and bridges depending on thespecific application of the processing system 3214 and the overalldesign constraints. The bus 3224 links together various circuitsincluding one or more processors and/or hardware components, representedby the processor 3204, the components 3104, 3106, 3108, 3110, 3112 andthe computer-readable medium/memory 3206. The bus 3224 may also linkvarious other circuits such as timing sources, peripherals, voltageregulators, and power management circuits, which are well known in theart, and therefore, will not be described any further.

The processing system 3214 may be coupled to a transceiver 3210. Thetransceiver 3210 is coupled to one or more antennas 3220. Thetransceiver 3210 provides a means for communicating with various otherapparatus over a transmission medium. The transceiver 3210 receives asignal from the one or more antennas 3220, extracts information from thereceived signal, and provides the extracted information to theprocessing system 3214, specifically the reception component 3104. Inaddition, the transceiver 3210 receives information from the processingsystem 3214, specifically the transmission component 3110, and based onthe received information, generates a signal to be applied to the one ormore antennas 3220. The processing system 3214 includes a processor 3204coupled to a computer-readable medium/memory 3206. The processor 3204 isresponsible for general processing, including the execution of softwarestored on the computer-readable medium/memory 3206. The software, whenexecuted by the processor 3204, causes the processing system 3214 toperform the various functions described supra for any particularapparatus. The computer-readable medium/memory 3206 may also be used forstoring data that is manipulated by the processor 3204 when executingsoftware. The processing system 3214 further includes at least one ofthe components 3104, 3106, 3108, 3110, 3112. The components may besoftware components running in the processor 3204, resident/stored inthe computer readable medium/memory 3206, one or more hardwarecomponents coupled to the processor 3204, or some combination thereof.The processing system 3214 may be a component of the UE 350 and mayinclude the memory 360 and/or at least one of the TX processor 368, theRX processor 356, and the controller/processor 359.

In one configuration, the apparatus 3102/3102′ for wirelesscommunication includes means for receiving a beam modification commandthat indicates a set of transmit beam indexes corresponding to a set oftransmit beams of a base station, and each transmit beam index of theset of transmit beam indexes may indicate at least a transmit directionfor transmitting a transmit beam by the base station. The apparatus3102/3102′ may include means for determining a set of receive beamindexes corresponding to receive beams of the apparatus based on the setof transmit beam indexes, each receive beam index of the set of receivebeam indexes indicating at least a receive direction for receiving areceive beam by the apparatus 3102/3102′. The apparatus 3102/3102′ mayfurther include means for receiving, from the base station, a BRRSthrough at least one receive beam corresponding to at least one receivebeam index included in the set of receive beam indexes.

In an aspect, the means for receiving, from the base station, the BRRSthrough the at least one receive beam corresponding to the at least onereceive beam index included in the set of receive beam indexes isconfigured to receive a first portion of the BRRS in a first set ofsymbols through a first receive beam corresponding to a first receivebeam index included in the set of receive beam indexes, and furtherconfigured to receive a second portion of the BRRS in a second set ofsymbols through a second receive beam corresponding to a second receivebeam index included in the set of receive beam indexes.

In an aspect, the BRRS is received in one or more symbols correspondingto one or more symbol indexes. In an aspect, the beam modificationcommand indicates the one or more symbol indexes, and a correspondingtransmit beam index of the set of transmit beam indexes for each symbolindex of the one or more symbol indexes. In an aspect, the one or moresymbol indexes in which the BRRS is received are predetermined. In anaspect, the BRRS is received through the set of transmit beams from thebase station corresponding to the set of transmit beam indexes. In anaspect, the BRRS is received through a different set of transmit beamsfrom the base station than the set of transmit beams corresponding tothe set of transmit beam indexes, the different set of transmit beamscorresponding to a second set of transmit beam indexes different fromthe set of transmit beam indexes.

In an aspect, the beam modification command is received in a MAC CE. Inan aspect, the beam modification command is received in a DCI message.In an aspect, the beam modification command is received via RRCsignaling. In an aspect, beam modification command is carried on aPDCCH.

The aforementioned means may be one or more of the aforementionedcomponents of the apparatus 3102 and/or the processing system 3214 ofthe apparatus 3102′ configured to perform the functions recited by theaforementioned means. As described supra, the processing system 3214 mayinclude the TX Processor 368, the RX Processor 356, and thecontroller/processor 359. As such, in one configuration, theaforementioned means may be the TX Processor 368, the RX Processor 356,and the controller/processor 359 configured to perform the functionsrecited by the aforementioned means.

It is understood that the specific order or hierarchy of blocks in theprocesses/flowcharts disclosed is an illustration of exemplaryapproaches. Based upon design preferences, it is understood that thespecific order or hierarchy of blocks in the processes/flowcharts may berearranged. Further, some blocks may be combined or omitted. Theaccompanying method claims present elements of the various blocks in asample order, and are not meant to be limited to the specific order orhierarchy presented.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but is to be accorded the full scope consistentwith the language claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” The word “exemplary” is used hereinto mean “serving as an example, instance, or illustration.” Any aspectdescribed herein as “exemplary” is not necessarily to be construed aspreferred or advantageous over other aspects. Unless specifically statedotherwise, the term “some” refers to one or more. Combinations such as“at least one of A, B, or C,” “one or more of A, B, or C,” “at least oneof A, B, and C,” “one or more of A, B, and C,” and “A, B, C, or anycombination thereof” include any combination of A, B, and/or C, and mayinclude multiples of A, multiples of B, or multiples of C. Specifically,combinations such as “at least one of A, B, or C,” “one or more of A, B,or C,” “at least one of A, B, and C,” “one or more of A, B, and C,” and“A, B, C, or any combination thereof” may be A only, B only, C only, Aand B, A and C, B and C, or A and B and C, where any such combinationsmay contain one or more member or members of A, B, or C. All structuraland functional equivalents to the elements of the various aspectsdescribed throughout this disclosure that are known or later come to beknown to those of ordinary skill in the art are expressly incorporatedherein by reference and are intended to be encompassed by the claims.Moreover, nothing disclosed herein is intended to be dedicated to thepublic regardless of whether such disclosure is explicitly recited inthe claims. The words “module,” “mechanism,” “element,” “device,” andthe like may not be a substitute for the word “means.” As such, no claimelement is to be construed as a means plus function unless the elementis expressly recited using the phrase “means for.”

What is claimed is:
 1. A method of wireless communication for a userequipment (UE), the method comprising: receiving a beam modificationcommand that indicates a set of transmit beam indexes corresponding to aset of transmit beams associated with a base station, each transmit beamindex of the set of transmit beam indexes indicating at least a transmitdirection for transmitting a transmit beam by the base station; andreceiving, based on the beam modification command, a reference signalfrom the base station using at least one receive beam, wherein a firstportion of the reference signal is received in a first set of symbolsand a second portion of the reference signal is received in a second setof symbols.
 2. The method of claim 1, wherein the receiving thereference signal using the at least one receive beam comprises:receiving the first portion of the reference signal in the first set ofsymbols using a first receive beam of the at least one receive beam; andreceiving the second portion of the reference signal in the second setof symbols using a second receive beam of the at least one receive beam.3. The method of claim 1, wherein the beam modification commandindicates a first set of symbol indexes corresponding to the first setof symbols and a second set of symbol indexes corresponding to thesecond set of symbols.
 4. The method of claim 3, wherein the beammodification command indicates a first correspondence between a firsttransmit beam index of the set of transmit beam indexes and the firstset of symbol indexes, and the beam modification command indicates asecond correspondence between a second transmit beam index of the set oftransmit beam indexes and the second set of symbol indexes.
 5. Themethod of claim 1, further comprising: identifying the at least onereceive beam based on at least one transmit beam index of the set oftransmit beam indexes.
 6. The method of claim 1, wherein the beammodification command is included in one of a medium access controlelement (MAC) control element (CE) or a downlink control indicator (DCI)message.
 7. The method of claim 1, wherein the reference signalcomprises one of a channel-state information reference signal (CSI-RS)or a demodulation reference signal (DM-RS).
 8. A method of wirelesscommunication for a base station, the method comprising: sending a beammodification command that indicates a set of transmit beam indexescorresponding to a set of transmit beams associated with the basestation, each transmit beam index of the set of transmit beam indexesindicating at least a transmit direction for transmitting a transmitbeam by the base station; and sending, in association with the beammodification command, a reference signal using at least one transmitbeam of the set of transmit beams, wherein a first portion of thereference signal is sent in a first set of symbols and a second portionof the reference signal is received in a second set of symbols.
 9. Themethod of claim 8, wherein the sending the reference signal using the atleast one transmit beam of the set of transmit beams comprises: sendingthe first portion of the reference signal in the first set of symbolsusing a first transmit beam of the set of transmit beams; and sendingthe second portion of the reference signal in the second set of symbolsusing a second transmit beam of the set of transmit beams.
 10. Themethod of claim 8, wherein the beam modification command indicates afirst set of symbol indexes corresponding to the first set of symbolsand a second set of symbol indexes corresponding to the second set ofsymbols.
 11. The method of claim 10, wherein the beam modificationcommand indicates a first correspondence between a first transmit beamindex of the set of transmit beam indexes and the first set of symbolindexes, and the beam modification command indicates a secondcorrespondence between a second transmit beam index of the set oftransmit beam indexes and the second set of symbol indexes.
 12. Themethod of claim 8, further comprising: determining the set of transmitbeams to be used for transmitting the reference signal.
 13. The methodof claim 8, wherein the beam modification command is included in one ofa medium access control element (MAC) control element (CE) or a downlinkcontrol indicator (DCI) message.
 14. The method of claim 8, wherein thereference signal comprises one of a channel-state information referencesignal (CSI-RS) or a demodulation reference signal (DM-RS).
 15. Anapparatus to be included in a user equipment (UE), the apparatuscomprising: means for receiving a beam modification command thatindicates a set of transmit beam indexes corresponding to a set oftransmit beams associated with a base station, each transmit beam indexof the set of transmit beam indexes indicating at least a transmitdirection for transmitting a transmit beam by the base station; andmeans for receiving, based on the beam modification command, a referencesignal from the base station using at least one receive beam, wherein afirst portion of the reference signal is received in a first set ofsymbols and a second portion of the reference signal is received in asecond set of symbols.
 16. The apparatus of claim 15, wherein the meansfor receiving the reference signal using the at least one receive beamis configured to: receive the first portion of the reference signal inthe first set of symbols using a first receive beam of the at least onereceive beam; and receive the second portion of the reference signal inthe second set of symbols using a second receive beam of the at leastone receive beam.
 17. The apparatus of claim 15, wherein the beammodification command indicates a first set of symbol indexescorresponding to the first set of symbols and a second set of symbolindexes corresponding to the second set of symbols.
 18. The apparatus ofclaim 17, wherein the beam modification command indicates a firstcorrespondence between a first transmit beam index of the set oftransmit beam indexes and the first set of symbol indexes, and the beammodification command indicates a second correspondence between a secondtransmit beam index of the set of transmit beam indexes and the secondset of symbol indexes.
 19. The apparatus of claim 15, furthercomprising: means for identifying the at least one receive beam based onat least one transmit beam index of the set of transmit beam indexes.20. The apparatus of claim 15, wherein the beam modification command isincluded in one of a medium access control element (MAC) control element(CE) or a downlink control indicator (DCI) message.
 21. The apparatus ofclaim 15, wherein the reference signal comprises one of a channel-stateinformation reference signal (CSI-RS) or a demodulation reference signal(DM-RS).
 22. An apparatus to be included in a base station, theapparatus comprising: means for sending a beam modification command thatindicates a set of transmit beam indexes corresponding to a set oftransmit beams associated with the base station, each transmit beamindex of the set of transmit beam indexes indicating at least a transmitdirection for transmitting a transmit beam by the base station; andmeans for sending, in association with the beam modification command, areference signal using at least one transmit beam of the set of transmitbeams, wherein a first portion of the reference signal is sent in afirst set of symbols and a second portion of the reference signal isreceived in a second set of symbols.
 23. The apparatus of claim 22,wherein the means for sending the reference signal using the at leastone transmit beam of the set of transmit beams is configured to: sendthe first portion of the reference signal in the first set of symbolsusing a first transmit beam of the set of transmit beams; and send thesecond portion of the reference signal in the second set of symbolsusing a second transmit beam of the set of transmit beams.
 24. Theapparatus of claim 22, wherein the beam modification command indicates afirst set of symbol indexes corresponding to the first set of symbolsand a second set of symbol indexes corresponding to the second set ofsymbols.
 25. The apparatus of claim 24, wherein the beam modificationcommand indicates a first correspondence between a first transmit beamindex of the set of transmit beam indexes and the first set of symbolindexes, and the beam modification command indicates a secondcorrespondence between a second transmit beam index of the set oftransmit beam indexes and the second set of symbol indexes.
 26. Theapparatus of claim 22, further comprising: means for determining the setof transmit beams to be used for transmitting the reference signal. 27.The apparatus of claim 22, wherein the beam modification command isincluded in one of a medium access control element (MAC) control element(CE) or a downlink control indicator (DCI) message.
 28. The apparatus ofclaim 22, wherein the reference signal comprises one of a channel-stateinformation reference signal (CSI-RS) or a demodulation reference signal(DM-RS).
 29. An apparatus to be included in a user equipment (UE), theapparatus comprising: a memory; and at least one processor coupled tothe memory and configured to: receive a beam modification command thatindicates a set of transmit beam indexes corresponding to a set oftransmit beams associated with a base station, each transmit beam indexof the set of transmit beam indexes indicating at least a transmitdirection for transmitting a transmit beam by the base station; andreceive, based on the beam modification command, a reference signal fromthe base station using at least one receive beam, wherein a firstportion of the reference signal is received in a first set of symbolsand a second portion of the reference signal is received in a second setof symbols.
 30. The apparatus of claim 29, wherein the reception of thereference signal using the at least one receive beam comprises to:receive the first portion of the reference signal in the first set ofsymbols using a first receive beam of the at least one receive beam; andreceive the second portion of the reference signal in the second set ofsymbols using a second receive beam of the at least one receive beam.31. The apparatus of claim 29, wherein the beam modification commandindicates a first set of symbol indexes corresponding to the first setof symbols and a second set of symbol indexes corresponding to thesecond set of symbols.
 32. The apparatus of claim 31, wherein the beammodification command indicates a first correspondence between a firsttransmit beam index of the set of transmit beam indexes and the firstset of symbol indexes, and the beam modification command indicates asecond correspondence between a second transmit beam index of the set oftransmit beam indexes and the second set of symbol indexes.
 33. Theapparatus of claim 29, wherein the at least one processor is furtherconfigured to: identify the at least one receive beam based on at leastone transmit beam index of the set of transmit beam indexes.
 34. Theapparatus of claim 29, wherein the beam modification command is includedin one of a medium access control element (MAC) control element (CE) ora downlink control indicator (DCI) message.
 35. The apparatus of claim29, wherein the reference signal comprises one of a channel-stateinformation reference signal (CSI-RS) or a demodulation reference signal(DM-RS).
 36. An apparatus to be included in a base station, theapparatus comprising: a memory; and at least one processor coupled tothe memory and configured to: send a beam modification command thatindicates a set of transmit beam indexes corresponding to a set oftransmit beams associated with the base station, each transmit beamindex of the set of transmit beam indexes indicating at least a transmitdirection for transmitting a transmit beam by the base station; andsend, in association with the beam modification command, a referencesignal using at least one transmit beam of the set of transmit beams,wherein a first portion of the reference signal is sent in a first setof symbols and a second portion of the reference signal is received in asecond set of symbols.
 37. The apparatus of claim 36, wherein the atleast one processor configured to send the reference signal using the atleast one transmit beam of the set of transmit beams is configured to:send the first portion of the reference signal in the first set ofsymbols using a first transmit beam of the set of transmit beams; andsend the second portion of the reference signal in the second set ofsymbols using a second transmit beam of the set of transmit beams. 38.The apparatus of claim 36, wherein the beam modification commandindicates a first set of symbol indexes corresponding to the first setof symbols and a second set of symbol indexes corresponding to thesecond set of symbols.
 39. The apparatus of claim 38, wherein the beammodification command indicates a first correspondence between a firsttransmit beam index of the set of transmit beam indexes and the firstset of symbol indexes, and the beam modification command indicates asecond correspondence between a second transmit beam index of the set oftransmit beam indexes and the second set of symbol indexes.
 40. Theapparatus of claim 36, wherein the at least one processor is furtherconfigured to: determine the set of transmit beams to be used fortransmitting the reference signal.
 41. The apparatus of claim 36,wherein the beam modification command is included in one of a mediumaccess control element (MAC) control element (CE) or a downlink controlindicator (DCI) message.
 42. The apparatus of claim 36, wherein thereference signal comprises one of a channel-state information referencesignal (CSI-RS) or a demodulation reference signal (DM-RS).
 43. Acomputer-readable medium storing computer-executable code for wirelesscommunication by a user equipment (UE), comprising code to: receive abeam modification command that indicates a set of transmit beam indexescorresponding to a set of transmit beams associated with a base station,each transmit beam index of the set of transmit beam indexes indicatingat least a transmit direction for transmitting a transmit beam by thebase station; and receive, based on the beam modification command, areference signal from the base station using at least one receive beam,wherein a first portion of the reference signal is received in a firstset of symbols and a second portion of the reference signal is receivedin a second set of symbols.
 44. A computer-readable medium storingcomputer-executable code for wireless communication by a base station,comprising code to: send a beam modification command that indicates aset of transmit beam indexes corresponding to a set of transmit beamsassociated with the base station, each transmit beam index of the set oftransmit beam indexes indicating at least a transmit direction fortransmitting a transmit beam by the base station; and send, inassociation with the beam modification command, a reference signal usingat least one transmit beam of the set of transmit beams, wherein a firstportion of the reference signal is sent in a first set of symbols and asecond portion of the reference signal is received in a second set ofsymbols.